Around 30 people - including young children - were rescued from the River Thames when the amphibious vehicle they were travelling on caught fire near the Houses of Parliament.
Firefighters from the London Fire Brigade's fire boat and firefighters on the land extinguished the blaze and around 30 people who had jumped into the water were quickly rescued.
The brigade was called to the blaze at 11.55am on Sunday morning and the first crews were on the scene before midday.
"A number of people jumped into the water but they were soon rescued and fortunately at this stage it doesn't look like anyone's been seriously injured," said group manager Neil Withers from the London Fire Brigade.
"People are clearly cold, wet and in shock but they were pulled from the water really quickly and that's testament to the work of our firefighters, other emergency rescue teams and others who rushed to the scene to help.
"People were rescued by firefighters, the RNLI, police officers and other non-emergency boats were also nearby and assisted in the rescue operation.
"The casualties, who are tourists, are being looked after by the London Ambulance Service and firefighters, who are keeping them warm and making them cups of tea.
"The damaged boat was pulled away from the scene by our fire boat and a full investigation into exactly what happened will now be taking place."
Tourists arriving at the Duck Tours bus stop in Chicheley Street near the London Eye on Sunday afternoon continued to board the yellow amphibious vehicles but were told that their tour would be land-based and the craft would not be entering the Thames.
The company offered ticket-holders a 50 per cent refund on their tickets.
London Duck Tours runs a fleet of the DUKW vehicles which enter and leave the Thames using a slipway at Lacks Dock next to the MI6 building on Albert Embankment.
The first DUKW tours began on the Thames 13 years ago.