Drug agents are investigating how a 20-pound bale of marijuana got mixed in with a truckload of watermelons that were delivered to the Good Shepherd Food-Bank (search).

A volunteer came across the marijuana (search) while picking through the watermelons Thursday afternoon. The man said the marijuana, which was neatly wrapped with packing tape, was loaded near the front end of a tractor-trailer that was delivering the watermelons to the food bank's warehouse.

After the bale was discovered, the Maine Drug Enforcement Agency (search) was called. An agent quizzed the man who found the bale but quickly determined he had nothing to do with the illegal shipment.

"It was definitely bizarre," the volunteer, who didn't want to be identified, told the Sun Journal of Lewiston.

When investigators came to the warehouse, the bale had been unloaded and the truck driver was gone.

Agents said they were looking for the driver in the Boston area, but they don't think he had anything to do with the marijuana, either.

More likely, a drug trafficker thousands of miles away in Mexico loaded the pot and either forgot about it or was forced to abandon the shipment, they said. The source of the pot isn't expected to be located.

The bale was seized as evidence and will likely be destroyed, investigators said. Police estimated the street value at about $20,000.

Good Shepherd Food-Bank distributes food to more than 470 food pantries and soup kitchens in Maine. Last year, the group distributed more than 9 million pounds of food.

Volunteers sort food that is donated from supermarkets and other sources, throwing away the products that cannot be eaten. The rest feed an estimated 50,000 people each month.