MARBLEHEAD — A dead humpback whale was discovered floating near the shore of Preston Beach Thursday evening.

When the National Marine Fisheries Service was notified, it sent Marine Mammal Rescue to the scene to conduct an external exam, measurement, and take photos of the corpse. Multiple crowds gathered to observe the dead whale on Friday.

According to MMR Director of Marine Mammal Conservation Ashley Stokes, the dead whale was a 41.7-foot-long female. Stokes said that whales are considered adults when they reach 42 feet in length.

The initial exam revealed no obvious cause of death.

“There’s really no smoking gun,” Stokes said. “She looks pretty good externally.”

Linear impressions were found on the whale’s body, which Stokes said likely indicates past entanglement wounds. However, she said she does not believe that was a cause of its death.

Stokes said that the mortality rate among humpback whales is currently higher than normal. She gave the example of morbillivirus, a disease, as a possible reason for the whale’s death. Stokes named incidental human interaction as another potential cause.

“Sometimes it’s a combination of things. The animal could have already been sick and then it gets hit by a ship because it’s debilitated,” Stokes said.

She said that DNA samples taken from the whale will help determine whether it was sick or not, as well as identify it more specifically.

“Humpback whales can be ID’d by the markings on the underside of their tail just like our fingerprints,” Stokes explained.

Stokes’ hope is that the whale can be removed from the ocean to have a full necropsy performed.

In addition to Stokes’ team, the state Environmental Police, animal control, and both the Marblehead and Swampscott police departments were present.

Stokes advised residents to keep their distance from the whale as long as it remains on the beach.