PORTLAND (AP) – The Coast Guard said Saturday checks by federal, state and local agencies found no additional oil in the Fore River near the Casco Bay Bridge and concluded that oil that had been found dissipated overnight.

A pilot boat operator had called the Coast Guard at 8:52 p.m. Friday after detecting a heavy, black crude oil in the river.

The source of the spill was not immediately determined.

“It was difficult last night trying to figure out how big a spill this was,” Capt. Jim McPherson, commander of Sector Northern New England, said in a statement Saturday.

“We had vessels under way all night trying to find the source of the spill. The good news is the spill has broken up and dissipated, and we have determined that there is no threat of additional oil leaking into the river,” McPherson said.