A humpback whale spotted in the Thames over the weekend has died, marine experts who were tracking its movements have said.

Volunteers from British Divers Marine Life Rescue (BDMLR) said they saw the body of the animal floating lifeless in the river near Greenhithe in Kent.

BDMLR (@BDMLR) Terribly sad news that soon after 5pm today the humpback whale which had not been seen in the Thames all day, was found dead around the Greenhithe area. Hopefully tomorrow a necropsy will be carried out to determine the cause of death #thameswhale #HumpbackWhale

The group had said there had been no sightings on Tuesday and appealed for information from people nearby.

A team of three volunteers began tracking the animal on Sunday morning, saying it surfaced near them within about 30 minutes of their arrival in the area of the Dartford crossing in Kent.

“The whale came into sight, slowly surfacing on the Dartford side of the bridge, and then diving again for around five minutes,” they said. “This pattern continued for a further few hours and the team followed the whale’s progress by land eastwards down the estuary.

“Once the whale reached Grays on the Essex side of the estuary, it slowed down and didn’t swim any further. The whale appeared to be moving at a steady pace, surfacing every five to six minutes and then diving again.”

They said they had received reports that the animal was in trouble in shallow water and concluded it had travelled westwards with the incoming tide.

On Tuesday morning, BDMLR appealed for information but later confirmed that the animal had been seen dead at about 5pm.

BDMLR (@BDMLR) The Cetacean Stranding Investigation Programme (CSIP) will carry out the necropsy as soon as it’s possible, they will then publish their findings.

The humpback whale was thought by the Port of London Authority to measure around 10 metres (33ft) in length. The Port of London Authority will attempt to recover the animal’s body for examinations by whale experts. A member of the species was spotted in the Channel last week, according to BDMLR, but it is not clear whether this was the same one.

Last year, a beluga whale, nicknamed Benny the Beluga, spent more than three months in the Thames. It is thought to have made its own way back out to sea in the new year.