Two dead whales have been found on Island beaches since Monday morning.

A decomposing humpback whale was seen beached but still in the surf on South Beach Monday, and a second humpback was found on East Beach on Chappaquiddick Tuesday morning.

The cause of death for each whale is still unknown, but it appears both of the decomposing whales have been dead for at least a few days, said Ainsley Smith, the regional marine mammal stranding coordinator with National Oceanic and Atmospheric Administration fisheries office.

Ms. Smith said NOAA was in communication with The Trustees of Reservations regarding the whale on East Beach and with the property owners for the whale on South Beach.

“They're the ones who have the ultimate choice,” she said, explaining that the property owners will decide whether to bury, move or leave the whales on the beaches.

Though it’s not clear how these whales died, many whales found stranded in the past seem to have been struck by vessels, Ms. Smith said.

Because they have been dead for several days, it's unlikely these humpbacks were the ones seen swimming off South Beach Sunday, Ms. Smith said.