Officers have said they are "extremely concerned" for the welfare of two men who are believed to have entered a river in Hull on Friday evening following a chase.
Humberside Police said officers had noticed a vehicle with a defective rear brake light at about 20:25 GMT. The vehicle had failed to stop for them, resulting in a pursuit.
Five minutes later, the vehicle crashed into a wall in Charlotte Street, the force said.
Two men then fled on foot and entered the River Hull, prompting a major search involving HM Coastguard, firefighters and a police underwater search team.
Charlotte Street is off George Street, close to North Bridge.
Det Insp Andy Crawforth said: "Following reports of two men entering the water, a search was immediately launched to locate and identify them.
"We are extremely concerned for their welfare and are conducting extensive lines of enquiries in an attempt to identify and locate them."
Det Insp Crawforth said there would be an increased police presence in the area over the weekend.
He added: "To help with these enquiries, I would ask anyone who believes they know who these men are, or who thinks that someone they know went missing yesterday evening, to contact us immediately."
