Montville ― The cleanup of a 1,200-gallon diesel spill in the Thames River from a ship that works on offshore wind projects continued on Thursday.

The spill occurred shortly after 1 p.m. Wednesday at Gateway Terminal during the refueling of the Atlantic Oceanic, a 165-foot tug and supply ship that was recently working on the construction of an offshore wind farm in Massachusetts.

While a boom around the vessel halted the flow of most of the fuel, state environmental officials said some fuel did escape into the river. Kropp Environmental Services responded to help contain the diesel and vacuum it from a truck on shore.

On Thursday, DEEP spokesman Paul Copleman said the cleanup work involved vacuuming and skimming the spilled fuel in the river. He said the “vast majority” of the fuel has been recovered. There continues to be absorbent boom protecting the shore.

“There remains an observable sheen in the water, but it is expected that natural attenuation from the sun and wave action will break up the sheen over the next few days,” Copleman said.

“We do not anticipate damage to nearby fisheries or aquaculture,” he said.

The Atlantic Oceanic was cleared to leave the scene on Thursday.

The investigation into the spill is being conducted by DEEP and Coast Guard.