Oregon is producing three times more marijuana than it can consume

Oregon is producing three times more marijuana than it can consume with “formidable” amounts now ending up on the black market, officials have warned.

US Attorney Billy Williams told law enforcement representatives from across the US on Friday that the state, where recreational cannabis use is legal, had a serious overproduction problem.

Mr Williams said officials needed a "bottom-line answer" on how much excess marijuana was being produced and how much of it ends up on the black market.

In pictures: 4/20 Marijuana world rallies

25 show all In pictures: 4/20 Marijuana world rallies

1/25 A man wears a marijuana leaf mask during the annual 4/20 cannabis culture celebration at Sunset Beach in Vancouver, British Columbia AP

2/25 A lady smokes marijuana on Parliament Hill on 4/20 in Ottawa, Ontario Getty Images

3/25 James Reed smokes a joint during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images

4/25 People sign a 4/20 sign on Parliament Hill on in Ottawa, Ontario Getty Images

5/25 A woman smokes marijuana on Parliament Hill on 4/20 in Ottawa, Ontario. Polling released showed strong support in Canada for a government drive to legalise recreational use of marijuana, but many would like the proposed minimum age for consumption to be raised. Sixty-three percent of respondents told the Angus Reid Institute they support legalisation Getty Images

6/25 A man smokes marijuana during the annual 4/20 marijuana rally on Parliament Hill in Ottawa, Ontario, Canada Reuters

7/25 Demonstrators smoke marijuana during the '4/20 Santiago' rally in favour of legalisation in front of the La Moneda presidential palace in Santiago, as part of the Global Marijuana March which is being held in hundreds of cities worldwide Getty Images

8/25 People play with a mock marijuana joint during a 4/20 party to demand legalisation and to celebrate marijuana culture outside the Senate building in Mexico City, Mexico Reuters

9/25 Adam Eidinger, co-founder of DCMJ, hands out free marijuana joints to DC residents who worked on Capitol Hill as part of the 1st Annual Joint Session to mark '4/20' day and promote legalising marijuana on Capitol Hill in Washington, DC Getty Images

10/25 Police arrest Rachel Ramone Donlan after she handed out free marijuana joints to DC residents who worked on Capitol Hill as part of the 1st Annual Joint Session to mark '4/20' day and promote legalising marijuana on Capitol Hill in Washington, DC AFP/Getty Images

11/25 Police arrest Rachel Ramone Donlan after she handed out free marijuana joints to DC residents who worked on Capitol Hill as part of the 1st Annual Joint Session to mark '4/20' day and promote legalising marijuana on Capitol Hill in Washington, DC Getty Images

12/25 Thousands of people gather to smoke marijuana during the '420 Santiago'rally in front of the La Moneda presidential palace in Santiago Getty Images

13/25 People attend the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images

14/25 Kevin Barron and Lasean Moore of Raleigh, North Carolina, share a joint during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images

15/25 Nic Ruhl takes a pull on a giant hand rolled joint at precisely 4:20pm MDT during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images

16/25 Various cannabis paraphernalia on display at a vendor's stall during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images

17/25 Mo Banez, of Austin, Texas, lights a joint during the Denver 420 Rally at Civic Center Park in Denver, Colorado Getty Images

18/25 A man displays a large container of cannabis during the Denver 420 Rally at Civic Center Park in Denver, Colorado. The rally, held annually, is a celebration of both the legalisation of cannabis and cannabis culture. Colorado is one of twenty-six U.S. states along with the District of Columbia that has legalised the use of cannabis either recreationally or medically AFP/Getty Images

19/25 Sitting in small groups on mats shaded by trees in the Rose Garden just across from the Knesset, participants lit up as the clock struck 4:20 for the local version of the traditional worldwide April 20 pro-marijuana events, known as '420' rallies Getty Images

20/25 An Israeli smokes a marijuana joint in Jerusalem during a rally at the Rose garden Getty Images

21/25 Sitting in small groups on mats shaded by trees in the Rose Garden just across from the Knesset, participants lit up as the clock struck 4:20 for the local version of the traditional worldwide April 20 pro-marijuana events, known as '420' rallies Getty Images

22/25 An Israeli girl poses with a mock marijuana joint in Jerusalem during a rally at the Rose garden, to celebrate 420 and to express their defiance of current laws Getty Images

23/25 aelis pass around a marijuana joint in Jerusalem during a rally at the Rose garden, to celebrate 420 and to express their defiance of current laws Getty Images

24/25 An Israeli smokes a marijuana joint in Jerusalem during a rally at the Rose garden, to celebrate 420 and to express their defiance of current law Getty Images

25/25 An Israeli smokes a marijuana joint in Jerusalem on April 20, 2017 during a rally opposite the Knesset to celebrate 420 and express defiance of current laws AFP/Getty Images

In a local newspaper column last month, the attorney warned huge surpluses were attracting criminal networks, causing money laundering and drug violence.

Authorities in 16 other states have reported seizing marijuana produced in Oregon, while postal agents have intercepted more than 2,600 pounds of cannabis (1,179kg) and $1.2m (£850,000) in associated cash.

"Here's what I know in terms of the landscape here in Oregon and that is, we have an identifiable and formidable marijuana overproduction and diversion problem," Mr Williams told officials.

“Make no mistake about it, we are going to do something about it."

The summit had been called after Attorney General Jeff Sessions withdrew an Obama administration memo guiding states with legalised cannabis on how to avoid federal scrutiny.

Representatives from 13 other US attorney's offices were in attendance, as well as the FBI, the US Postal Inspection Service, US Forest Service and US Customs and Border Protection.

Oregon voters approved the sale of recreational marijuana in 2014 and it became legal the following year. The state has allowed the use of cannabis for medical purposes since 1998.

It now has 900 licensed recreational growers, with more than 1,100 licenses awaiting approval. Some 500 retailers are licenced to sell weed and another 250 applications are pending.

Advocates deny legalisation has caused a spike in black markets sales and instead claim legal cannabis is much easier to track.

However, former Oregon State University professor Seth Crawford told the summit the state had created the overproduction problem by not capping the number of recreational cannabis producers.

"If you were an investor and you had just dropped $4m into a [marijuana] grow and you had thousands of pounds of flower that was ready to go but you had nowhere to sell it, the only thing you can do is sell it on the black market.

"It was a system designed for failure. You created this huge industry that has nowhere to put its product."

He estimated Oregon growers produce up to three times the amount of marijuana that the state can absorb legally each year.

Leland Berger, an attorney who specialises in marijuana cases, said: "When I moved to Oregon in 1979, cannabis was a billion-dollar crop then, so the notion that this is somehow caused by legalisation or by the medical program is something that's misplaced."