PUEBLO, COLO. -- Pueblo Fire crews are working to contain fuel that has spilled into the downtown sewer system after an overflow early Monday morning.

Officials said a tanker truck was filling an underground tank near the intersection of 7th Street and Grand Avenue around 1:30 a.m. when the tank overflowed, spilling fewer than 100 gallons of gasoline into the storm sewer system.

Crews contained as much fuel as possible at that time but got a call from another downtown business later Monday morning saying they smelled gas near the Riverwalk.

Officials said the diesel fuel moved downstream into the sewer system that does under the Historic Arkansas Riverwalk Project (HARP). Crews are trying to absorb all the fuel at the lowest point of the channel between the Riverwalk and Runyon Lake.

Crews have closed the Runyon Lake recreational area while the cleanup is in process. Crews from the Pueblo City/County Health Department and the Colorado Division of Wildlife are assisting in the cleanup.