A tugboat sank off the coast of Kennebunk early Thursday after colliding with another tug that was towing it, Coast Guard officials said.

The Coast Guard said a crew member of the tugboat Helen Louise reported the collision about three miles south of Kennebunk late Wednesday night. The tug that sank, the Capt. Mackintire, had no crew on board and no one was injured, the Coast Guard said.

The Coast Guard sent two vessels in response to the report from the Helen Louise’s crew member.

It’s not yet clear how much diesel fuel has spilled, and a Coast Guard spokeswoman said the agency is hoping to set up a dive in the next few days to assess the condition of the Capt. Mackintire and determine if the vessel and its remaining fuel can be recovered.

Late Friday morning, Coast Guard officials confirmed that the two retired tugs collided while fuel was being transferred from the Mackintire to the Helen Louise.

There were two crew members aboard the Helen Louise, according to the Coast Guard. That tug was escorted to Portsmouth, New Hampshire, early Thursday without incident.

Another Coast Guard vessel, the 87-foot Reef Shark, began towing the 74-year-old Capt. Mackintire to Portland, but the Capt. Mackintire started taking on water and the crew cut the towline. It sank around 2 a.m. Thursday in about about 158 feet of water, Coast Guard officials said.

At the time of the collision, Coast Guard Petty Officer Cynthia Oldham said, the vessels were traveling in 6-foot swells and winds of about 12 knots, with visibility of 10 miles.

Kevin Battle, Portland’s harbor master, said Coast Guard officials told him the crew was transferring fuel from the Mackintire to the Helen Louise when the collision occurred. The Mackintire, he said, had several 55-gallon drums of fuel and a fuel bladder aboard as cargo. Coast Guard officials later confirmed that account after initially saying the cause of the collision was under investigation.

The Mackintire had been moored off Portland before setting out on its fateful voyage toward Portsmouth, Battle said.

Both the Capt. Mackintire and the Helen Louise are owned by Tim Whitney of Annapolis, Maryland, and the vessels were being transferred to him from Bar Harbor, Battle said. Whitney buys boats and fixes them up for use in movies and television, Battle said.

A message left for Whitney at his boat repair yard in Annapolis was not immediately returned Friday.

Battle said he was told that the Mackintire’s engines had seized up at some point. As the Helen Louise was attempting to tow the Mackintire from Bar Harbor to Portsmouth, it developed fuel problems near Casco Bay and came into the harbor for repairs. The Mackintire was temporarily moored off Portland’s East End before the two vessels continued on their voyage toward Portsmouth in recent days.

There was no sign that the tug was taking on water while it was moored off the eastern waterfront in Portland, Battle said. He said it broke loose from its mooring once, but was corralled by another tug in the harbor and returned to where it had been tied up.

Battle said the two vessels had been reclassified as personal watercraft, making them subject to less restrictive safety requirements than those that apply to working tugboats.

Coast Guard officials said they are “evaluating pollution potential” where the tug sank and said there were reports of a fuel sheen on the water in the area. But Oldham said Coast Guard aircraft have not spotted any sheens and another flight is scheduled for today.

The Mackintire’s fuel capacity is 12,000 gallons, Coast Guard officials said, but their reports indicate it had about 4,400 gallons aboard at the time of the collision.

Ray Billings, the harbormaster for Kennebunkport, said he alerted fishermen and other boaters in his town about the sinking and told them to be alert to the possibility of fuel sheens or floating barrels. He said none had been reported to him by late Friday morning.

The tug that sank was built in 1944 and operated originally in Florida. In 1969, it was bought by a tug company in Rhode Island and then sold in 1977 to a tugboat company in New London, Connecticut. That same year, it was sold to Winslow Marine in Southport and renamed the Marjorie J. Winslow. It was sold to the Eastport Port Authority in 2012, when it was renamed the Capt. Mackintire.

The Easport Port Authority sold it in 2014 to a buyer from Queensland, Australia, the port’s executive director, Chris Gardner said. He said he had no information on the tugboat after that sale.

This photo of the 80-foot tugboat Capt. Mackintire under tow off Portland was taken Wednesday. On Thursday it sank about 3 miles south of Kennebunk in about 158 feet of water. U.S. (Coast Guard photo)