Surrey Police said they were called to Sunbury Lock, near Wheatleys Eyot, at around 8.50am to reports of "a small boat capsizing".

South East Coast Ambulance Service (SECAMB) and Surrey Fire and Rescue also attended.

Rescuers are still searching for the missing person, and have asked the public to avoid the area.

An ambulance spokesperson said three of the five rescued from the river were taken to hospital for checks.

"We believe that there were six people involved in the incident, and five of these have been safely located," a police spokesperson added.

"We are working to locate the outstanding person.

"Sadly, we believe a man in his 60s may still be in the river," the force said in a statement.

"His relatives have been informed and are being kept updated."

Inquiries to establish the full circumstances of what happened are ongoing, police added.

Ch Insp Andy Jenkins said: "This is a very distressing time for all involved and we continue to support our partners in the search for the missing man.

"Our enquires to establish the exact circumstances of how the boat capsized remain underway but at this time we do not believe there to be any suspicious circumstances or third-party involvement."