Police are searching Eel Pie Island after a canoe believed to belong to missing teenager was found near the boat yard.

Police also cordoned off the car park beside the Thames at the end of Ham Street, Ham, where the blue Nelo canoe was brought ashore, and declared the area a crime scene.

It is believed the 17-year-old boy was taking part in the Richmond Hasler Marathon, which started at Ham House car park.

Police were first called at 12.25pm after a competitor did not finish a race.

At least 200 people were gathered at the scene, and a race organiser told spectators what happened, and asked any volunteers wanting to help search the river banks to approach the police.

He said racing had been suspended, and no trophies would be awarded today.

A number of day trippers enjoying the Sunday afternoon sunshine continued their picnics near the car park oblivious to the situation, and music could be heard coming from Ham House.

However, by about 3pm police had cleared the area, and a police boat, helicopter and boats from the RNLI lifeboat station at Teddington were searching the river.

Police closed Eel Pie Island at 5pm to allow a police dog to search it without the contamination of other people’s scents.

Entrants to the event, organised by the Richmond Canoe Club, had to be members of the British Canoe Union.

A police spokesman said: “We were called following reports of a person in the river.

“Officers from Richmond, the air support unit and the marine policing unit, along with the coastguard, are in attendance and are trying to locate the missing person, believed to be a 17-year-old boy.

“Next of kin have been informed.

“The boy is believed to have capsized from his canoe.”

Did you see what happened? Email martingeorge@london.newswquest.co.uk