A rescue operation is under way in Liverpool after an amphibious tour bus with 30 passengers on board sank in the Albert Dock.
One of Liverpool's fleet of Yellow Duckmarine tour buses began sinking just before 4pm today in Salthouse Dock at the front of the Albert Dock complex.
A spokesman for the Maritime and Coastguard Agency said 30 passengers were on board.
It is understood that most of that number have now been accounted for, but a rescue operation involving police, fire, ambulance and coastguard crews is under way to find the remaining passengers.
The incident is the second sinking involving one of the vessels this year.
The last time it happened was in March and following that incident the buses' permission to go in to the water was suspended while an investigation was carried out.
A spokeswoman for the North West Ambulance Service said there had been no fatalities and that 31 people had been rescued.
One man was taken to hospital as a precaution and the incident was now being "scaled back," the spokeswoman said.
She added: "We are unaware that there is anybody unaccounted for but police are continuing to search the water just to see if there is anybody else affected and we are on stand-by."
Firefighters rescued three people from the water, a spokesman for Merseyside Fire and Rescue Service said.
Chief Fire Officer Dan Stephens said: "Three people have been rescued by firefighters from the water. We have had assistance from a number of agencies on scene. We are working with police, ambulance and coastguard to account for everyone on board.
"All firefighters on Merseyside are trained in still water rescue to allow them to safely enter canals and lakes and dock areas, such as in this incident, to help rescue anyone in need."
The three rescued by firefighters were adults.
It is understood that some of the passengers had to be treated for shock but that no other major injuries have been reported.
Speaking on Twitter, the Mayor of Liverpool Joe Anderson refused to be drawn on the future of the yellow vessels until he knew everybody involved in the latest incident was safe.
He said: "Albert Dock Duck incident, look I will not make any official comment on future of these ducks until we know people are all ok+accounted for."
Mr Anderson later tweeted: "Albert Dock incident: police confirm 31 people entered the dock, 31 people have been accounted for. Everyone ok, some people still in hospital."
In May, the Queen had a ride on one of the yellow Duckmarine buses when she visited the region as part of her Diamond Jubilee tour to celebrate 60 years on the throne.