A tugboat carrying several fuel containers that was being towed to Portsmouth, New Hampshire, sank early Thursday after colliding with the tug that was towing it, Coast Guard officials said.

The collision occurred as fuel was being transferred from the Capt. Mackintire to the Helen Louise, the boat towing it, the Coast Guard said. The Capt. Mackintire was carrying diesel fuel in several drums and a fuel bladder, officials said.

The tugboat Capt. Mackintire is moored off Portland's Eastern Promenade in frigid weather in December. The vessel sank early Thursday after a collision with another tugboat that was towing it. The Capt. Mackintire had no crew on board and no one was injured, the Coast Guard reported. Photo by Jack Milton

The Capt. Mackintire had no crew on board and no one was injured, the Coast Guard said. It’s not yet clear how much diesel fuel spilled, and Coast Guard officials said they are “evaluating pollution potential” where the tug sank.

There were reports of a fuel sheen on the water in the area about three miles south of Kennebunk, but Coast Guard Petty Officer 2nd Class Cynthia Oldham said Coast Guard aircraft had not spotted any sheens and another flight was scheduled for Friday. 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 sunken tug and determine if it and any remaining fuel can be recovered.

There were two crew members aboard the Helen Louise, according to the Coast Guard, one of whom reported the collision late Wednesday.

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

At the time of the collision, Oldham said, the vessels were traveling through 6-foot swells with winds of about 12 knots and visibility of 10 miles.

The Helen Louise was escorted to Portsmouth, New Hampshire, early Thursday by a second Coast Guard vessel without incident.

Kevin Battle, Portland’s harbor master, said Coast Guard officials told him the Capt. Mackintire had several 55-gallon drums of fuel and a fuel bladder aboard.

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 Capt. Mackintire 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 toward Portsmouth on Wednesday.

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 remoored.

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.

The Mackintire’s fuel-tank 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.

Jim Black, the harbormaster for Kennebunkport, said he alerted fishermen and other boaters in his town about the sinking and told them to watch for fuel sheens or floating barrels. He said none had been reported by late Friday morning.

The Capt. Mackintire 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 and renamed the Capt. Mackintire.

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

Edward D. Murphy can be contacted at:

emurphy@pressherald.com