A man rolls a joint during a demonstration demanding the approval of the use of marijuana for medicinal and recreational purposes in front of the Mexican Senate building in Mexico City Pedro Pardo/ AFP

Workers at a charity shop in Monroe, Washington made an unexpected discovery last week (6 March) when they opened a donated cool box to discover nearly four ounces of weed inside.

The plastic box and the plastic baggies inside were donated to a Goodwill in the Pacific Northwest. The workers from the state immediately called the police when they made the discovery.

"(The) employees were surprised when they opened the lid," the police said in a tweet.

The local Fox news affiliate Q13 reported he cooler contained 3.75lbs of pot, with an estimated street value of $24,000.

The charity shop is now in the process of looking over its surveillance videos to see if they can identify the individual who dropped off the cooler.