BRANSON, Mo. (AP) — A boat carrying tourists on a Missouri lake capsized and sank Thursday night, killing at least eight people, the local sheriff said.

Stone County Sheriff Doug Rader said seven people were hospitalized and several others remain missing after a Ride the Ducks boat sank on Table Rock Lake in Branson. The exact number of those missing was not immediately available.

A spokeswoman for the Cox Medical Center Branson said four adults and three children arrived at the hospital shortly after the incident. Two adults are in critical condition and the others were treated for minor injuries, Brandei Clifton said.

Rader said the stormy weather was believed to be the cause of the capsizing.

Steve Lindenberg, a National Weather Service meteorologist in Springfield, Missouri, said the agency issued a severe thunderstorm warning for the Branson area Thursday evening. Lindenberg said winds reached speeds of more than 60 mph.

"It's a warning telling people to take shelter," he said.

Rader said an off-duty sheriff's deputy working security for the boat company helped rescue people after the accident.

Multiple dive teams from a number of law enforcement agencies were assisting in the rescue and recovery effort. Rader said crews would stay on the scene all night.

"It's going to be a challenging night and tomorrow," the sheriff said.

Suzanne Smagala with Ripley Entertainment, which owns Ride the Ducks in Branson, said the company was assisting authorities with the rescue effort. Smagala added this was the Branson tour's first accident in more than 40 years of operation.

Branson is about 200 miles (320 kilometers) southeast of Kansas City and is a popular vacation spot for families and other tourists looking for entertainment ranging from theme parks to live music.