At least 11 people drowned on Thursday when an amphibious "duck boat" capsized and sank in stormy weather on a lake in Missouri with 31 people, including children, on board, as divers searched for other possible victims, police said.

Seven people were taken to hospital following the incident on the "Ride the Ducks" amphibious vehicle on Table Rock Lake, near Branson, Missouri, Stone County Sheriff Doug Rader told reporters.

At least 11 people were killed in the incident as divers finished their search effort for the night and will start again in the morning, the sheriff said later in a news conference.

Emergency crews responded to the incident shortly after 7pm after thunderstorms rolled through the area, the fire district said on Twitter.

Video footage shot by an eyewitness who was on shore showed strong waves tossing two duck boats side to side. The video clip was posted online by KY3.

"Our number one priority is the families and our employees that were affected by this tragic accident; as of this time right now we are assisting the authorities as they continue with their search and rescue operation," said Suzanne Smagala-Potts a spokeswoman for Ripley Entertainment, which owns the Ride The Ducks operation in Branson.

She could not confirm how many crew members were aboard the boat.

Duck amphibious vehicles are used on sightseeing tours around the world and have been involved in a number of fatal accidents in the past two decades.

The company that builds ducks, Ride the Ducks International LLC, agreed in 2016 to pay a $1 million fine after one of the vehicles collided with a bus in Seattle, killing five international students.

The company admitted to failing to comply with US vehicle manufacturing rules.