PORTLAND – The Coast Guard is investigating whether the Scotia Prince struck bottom, causing the underside of the boat to crack and let seawater seep into a fuel tank.

The ship, which travels daily between Portland and Yarmouth, Nova Scotia, may have grounded over Canadian waters, said Cmdr. Roy Nash of the Coast Guard Marine Safety Office in Portland.

Canadian investigators told Nash on Tuesday the ship’s hull was likely punctured when the ferry left the deep-water channel while heading into Yarmouth Harbor.

Ships approaching a harbor must keep red buoys to the right and green buoys to the left to avoid any submerged obstacles, but Nash said the boat may have traveled on the wrong side and hit a submerged obstacle.

The damage allowed seawater to leak into the ship’s fuel oil before the problem was identified. There were no reports of spilled oil, he said.

A diver found the dent and crack and welded a plate over it during the stopover in Yarmouth. The ship has since continued its daily crossings.

Coast Guard investigators began looking into the incident after learning about it late last week. There had been no reports of the vessel striking anything during its operations, Nash said.

Local Coast Guard inspectors had planned to visit the ship later this week to follow up on the incident.

Jorg Walczak, operations manager for International Shipping Partners in Miami, the managers of the vessel, said the crew did not notice any collision. The damage was only noticed after water leaked into the fuel tanks, he said.

Walczak said he was not aware of the ship leaving the channel, and suggested the damage could have been from floating debris.