Search teams are trying to find a man who went missing after getting into difficulties in a river.
The unnamed man is believed to have got into trouble after entering the Jubilee River in Datchet, Berkshire, at around 7pm yesterday.
Members of the public who have tried to join the search mission have been told by police to stay out of the water to avoid getting into difficulties.
Thames Valley Police said "search activity" was being carried out in the water this morning as they appealed for witnesses to come forward.
Superintendent Kate Ford said: "It is understood that some members of the public are attempting to search near the Jubilee River for the man who is yet to be located.
"I would like to advise anyone who is doing this that they do not enter the water as this could put them in danger.
"They should search from the bank only and, if they see anything they think is significant, they should speak to a police officer at the scene."
Anyone with information about the missing man is asked to call Thames Valley Police on 101.