A man died and two other people were seriously injured after they were "thrown" from a vehicle and trailer when a bridge collapsed.
Police were called to a farm in the Moor Lane area of Roeburndale in Lancashire just before 4.30pm on Tuesday.
Ambulance crews, the fire service and mountain rescue also attended the scene.
Officers said 11 people were in the vehicle - reportedly a Polaris Ranger - and its trailer, which both fell into the river when the bridge gave way.
One man was pronounced dead at the scene after suffering fatal injuries, Lancashire Constabulary said.
A second man was taken to Royal Preston Hospital to be treated for a serious head injury.
A third person, who sustained a serious back injury, was taken to Royal Lancaster Infirmary, as were some others.
An investigation is under way and the Health and Safety Executive has been informed.
Detective Inspector Kirsty Wyatt said: "We believe the vehicle was pulling the trailer, containing a number of people, when a bridge gave way. Those people were then thrown from the vehicle and trailer.
"Our investigation is at very early stages and enquiries are ongoing to establish what happened."
Anyone with information is asked to call 101, quoting log 0953 of 18 January.