MONCTON, N.B. – The federal fisheries department is trying to figure out what caused the recent deaths of several endangered right whales in the waters off eastern Canada.

A fisheries official says at least five North Atlantic right whales were found dead in the Gulf of St. Lawrence this month — four of them in the past week — near Quebec's Magdalen Islands.

Biologist Cathy Merriman says the deaths are a serious blow to the endangered species, accounting for one per cent of the estimated 500 North Atlantic right whales believed to be living worldwide. She said it's too early to tell if the deaths are connected, but the department is doing everything it can to protect the remaining population.

"It has potential quite negative implications for the ability of that population to recover," Merriman said in an interview Saturday. "There's a lot of work and a lot of effort needed to try and understand what is happening, and hopefully it's something that can be prevented, but we really just know nothing right now."

The fisheries department has dispatched aircraft and Canadian Coast Guard vessels to locate, tag and get biological samples from the dead whales, and is looking into towing one of the carcasses to land so a post mortem can be conducted.

The department is working with partners Canada and the U.S. to find out what happened to prevent further deaths, said Merriman.

"There's no one agency or organization that can do this," she said. "It's a pretty complex operation that's going on right now to bring everyone's expertise together to make sure we do everything we can."