Researchers say preliminary findings show an endangered North Atlantic right whale may have been struck by a ship before the animal was found dead in Massachusetts waters.

Officials with the U.S. National Oceanic and Atmospheric Administration say bruising consistent with blunt trauma could be evidence of a ship strike.

The U.S. federal agency is urging vessels to keep a close watch for right whales, which often swim just below the water's surface and can be hard to see.

North Atlantic right whales are critically endangered; only a few hundred still exist in the world. In recent decades, a significant percentage of their deaths have come from being struck by ships or getting entangled in fishing nets.

The eight-metre-long, one-year-old female was found dead in Cape Cod Bay on Thursday and towed to a harbour where it could be placed on a flatbed for transport. A final analysis is expected to take weeks.

With files from CBC News