HALIFAX -- Injuries suffered by at least two of six North Atlantic right whales found floating lifeless in the Gulf of St. Lawrence appear to be consistent with ship strikes, marine mammal experts say.

Tonya Wimmer of the Marine Animal Response Society said Tuesday that the preliminary findings of necropsies on three of the whales indicate that two of them sustained blunt traumas that caused extensive bruising along their sides and internal hemorrhaging.

A third died after becoming snarled in fishing rope that wrapped around one flipper and inside its mouth.

She said the team of federal fisheries officials, veterinarians and other marine experts who were part of the necropsies in P.E.I. couldn't yet say conclusively what caused the deaths as they await results from biological testing on the animal's tissue. Experts are set to release a final report within the next two months.

Still, Wimmer said the information so far seems consistent with a collision with a vessel of some sort -- one of the most lethal hazards for the endangered animals.

"The animal was obviously struck by something large, what it could be we don't know," she said in Halifax. "When we've seen that in the past, it has been on animals where there have been vessel collisions, but for these two we don't know for a fact because no one saw these animals getting struck."

The six North Atlantic right whales -- among the most endangered large mammals on Earth -- were found dead and decomposing in waters north of Prince Edward Island and southeast of Quebec's Gaspe Peninsula last month.

The federal Department of Fisheries and Oceans said late Tuesday that although six carcasses were found, only three necropsies were planned given the other whales' advanced state of decomposition.

Pierre-Yves Daoust of the Atlantic Veterinary College in P.E.I. led the necropsies and said they discovered internal hemorrhaging confined to the thoracic cavity and some of the soft tissues.

"That suggests there may have been some major shearing forces that had ruptured blood vessels and caused fatal internal bleeding," he said. "What we saw is consistent with blunt trauma and therefore a ship strike ... but we can never completely rule out the possibility of some odd changes that may have happened after death."

Still, he said the lack of a conclusive cause of death shouldn't prevent officials from working to prevent future ship strikes while intensifying the research being done on the animals, which were hunted to the brink of extinction decades ago. The loss of six North Atlantic right whales represents about one per cent of the estimated 525 endangered animals now in existence.

"We cannot wait to have another half dozen right whales killed either this summer or next summer before we start addressing this potential cause of mortality," he said.

The loss of so many right whales so quickly was probably last seen when whaling decimated their population in the 19th century, said Mark Baumgartner at the Woods Hole Oceanographic Institute on Cape Cod. He also said the deaths should be a call to do more to protect the animals when possible.

Wimmer said more needs to be done to identify the whales' migratory routes and habitats so they can be protected against ship traffic and fishing activity. She said one of the whales -- a 13-metre-long female around 11 years old -- had fishing line and local buoys on it, so they may be able to determine where it travelled by locating the fisherman.

The other two were males, with one roughly 37 years old and 15 metres long and the other 14 metres long.

She said much is known about the North Atlantic right whales' presence in the Bay of Fundy, but there is less information about their shift to the Gulf of St. Lawrence and possibly other areas.

"We have to have a better understanding of how these entanglements happen, where they might happen, to then hopefully prevent it from happening," she said. "We don't know when and where they were harmed and that's the hard part because we need that information to go, 'OK, here's where we need to work and who we need to work with."'

Governments took steps to protect certain areas after it became clear that the whales transited through certain areas on their way to feeding grounds off the East Coast.

The International Maritime Organization years ago designated the Roseway Basin, southwest of Nova Scotia, as an area to be avoided to protect the whales. With that, ships were urged to steer clear of an area that measures 1,780 square nautical kilometres. The initiative came after the IMO approved a proposal by Ottawa in 2003 to amend shipping lanes and force vessels to divert several kilometres around feeding grounds in the Bay of Fundy.

Whale experts say the measures have helped protect the slow, lumbering animals against strikes and build up their population from a low of 350 a decade ago.