HMCS Athabaskan drifted for several hours off eastern Cape Breton last Friday after the tow line broke, said Capt. Doug Keirstead of the Royal Canadian Navy in Halifax.
Keirstead said there is damage to the hull behind the ship's identifying numbers, though he declined to say what the damage was and how it came about.
"At this point all I can say is that we are aware that there is damage visible," Keirstead said in an interview.
During the tow, the destroyer came into Sydney, N.S., harbour last Thursday, and then was towed out on Friday evening despite forecasts of a major storm.
Cmdr. Matthew Coates, the deputy chief of surface operations for the East Coast navy, said the decision to proceed was taken by the towing company, though navy officers were on board.
"You look at the weather conditions and at that time it was deemed appropriate they could conduct the tow," Coates said.
He said the navy will review whether the decision to continue the voyage was prudent.
"You never know when you need to learn from lessons, whether good, bad or indifferent, and therefore it's due diligence on our part to look at processes and see if it happened appropriately," Coates said.
He also declined to elaborate on the extent of the damage.
"The initial assessment is that it's not significant damage, but we need to allow the experts to do that assessment," he said.
Jean-Philippe Brunet, a spokesman for the Group Ocean Inc. towing firm, said in a telephone interview that the captain of the tug made the decision to tow HMCS Athabaskan around the shoals of Scatarie Island on Friday night.
Brunet said the navy officers on board were consulted about the decision.
"The navy was aware that it was kind of late in the year to do it, but it was not dangerous to do the towing," he said.
"The weather was OK. There was a window of 40 hours to do it and the weather was OK."
But he said the waves and winds turned out to be rougher than expected.
He said he couldn't comment on what caused the tow lines to detach from the vessel, but he added that the damage "probably" occurred during the attempts to re-attach it to the tug.
Keirstead said HMCS Athabaskan was being towed because scheduled repairs weren't completed on time and it had to be returned to Halifax before the St. Lawrence Seaway closed for the winter.
He said the vessel was supposed to have undergone a routine refit by the end of November last year and was expected to be capable of sailing after that work was done.
But Keirstead said the ship couldn't return to Halifax without assistance due to maintenance delays and other problems.
"The reason why Athabaskan is not returning under her own power is because there have been delays in some of the required maintenance and further unforeseen maintenance required," he said.
Charlie Payne, president of Seaway Marine and Industrial Inc. in St. Catharines, Ont., said the ship needed another three to four weeks of work before it could steam home under its own power.
Payne said his firm told the navy that towing the vessel was risky.
"We advised them of the various issues associated with the tows," he said. "It's a time of year when it's a difficult tow ... because of the weather."
Coates said the ship will remain in Sydney harbour until the hull damage has been assessed and officers determine how to safely return it to Halifax to complete the refit and repair the latest damage.
HMCS Athabaskan was commissioned on Sept. 30, 1972.
Note to readers: This is a corrected story. A previous version misspelt the name of Captain Doug Keirstead