Londoners were previously urged to stay away after a dolphin was spotted near Putney Bridge, in southwest London, and also near Hammersmith Bridge, in west London, on Thursday.

However, since then, two dolphins have been found dead on the bank of the Thames.

Authorities are now working to recover the animals.

One was said to have been found dead in Battersea and the other in Greenwich, The Evening Standard reported.

"We are aware of reports of two dolphins that sadly died," a Port of London Authority spokesperson told Sky News.

They added: "We are working with the Cetaceans Stranding Investigation Programme and will recover the animals."

Mary Tester, a volunteer with British Divers Marine Life Rescue (BDMLR), reportedly said she was concerned about the recent rise in the number of dolphins in the Thames.

"This is kind of a new phenomenon that seems to be increasing, and isn't really showing any signs of slowing up. Because it's new we don't have a rescue protocol in place for this," she told The Standard.

Previously, the dolphin was said to have been seen "struggling with the tide".

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Julia Cable, operations director at BDMLR, said the area in which the dolphin was seen was "too far really for a dolphin to be up the river."

She added: "The worst thing is if people start going up to it, it could disorient it more.

"They're used to being out in open water, with all of the noise on the river going on, for an animal it's very confusing."