BOSTON — Biologists blame a vessel strike for the death of a rare North Atlantic right whale calf in May.

The National Oceanic and Atmospheric Administration said a necropsy showed nine propeller or chop wounds on the whale’s belly, with several extending to the sides of the body and tail. There was no evidence of entanglement or major health issues.

The nearly 30-foot long, roughly 10,000-pound whale was found dead off Chatham, Cape Cod, on May 5. Experts had suspected a ship strike all along.

NOAA said because no witnesses or other conclusive evidence of vessel misconduct has been found the case has been closed.

There are only an estimated 450 to 500 North Atlantic right whales left in the world. Two of the 14 calves born last winter have died.