New London — About 350 gallons of diesel fuel spilled into the Thames River from the Cross Sound Ferry terminal Tuesday, according to the state Department of Energy and Environmental Protection.

McCarthy Fuel of Waterford accidentally overfilled the fuel system on the Sea Jet I, which is owned by Cross Sound Ferry, according to DEEP spokesman Dwayne Gardner.

“Cross Sound Ferry quickly deployed containment and absorbent boom,” he said. “An environmental contractor has been hired to recover the fuel.”

The spill was later stopped, Gardner said, and the ship will remain out of service until the spill is remediated. A “non-recoverable sheen” will remain inside the containment boom area.

“The non-recoverable sheen will naturally attenuate — no lasting harm to the environment,” Gardner said.

DEEP officials and the contractor will be on site today to remove the remaining boom, and the vessel will resume service, Gardner said.

The Sea Jet I, a 400-passenger ferry, was acquired by Cross Sound Ferry in 1995 and makes the 16-mile trip between New London and Orient Point in 40 minutes, according to the company’s website.