Divers searched a Missouri lake Friday for four people still missing after a duck boat packed with tourists capsized and sank in high winds, killing at least 13 people in the tourist town of Branson.
Authorities blamed stormy weather for the accident Thursday evening on Table Rock Lake. Winds at the time were blowing as hard as 65 mph, according to the National Weather Service.
Fourteen people survived, including seven who were injured when the boat went down, state police said.
Duck boats, named for their ability to travel on land and in water, have been involved in other deadly trips in the past. Five college students were killed in 2015 in Seattle when a duck boat collided with a bus, and 13 people died in 1999 when a boat sank near Hot Springs, Ark.
Safety advocates have sought improvements and complained that too many agencies regulate the boats with varying safety requirements.
The boats originally were designed for the military, specifically to transport troops and supplies in World War II. They later were modified for use as sightseeing vehicles.
Passengers on a nearby boat described the chaos as the winds picked up and the water turned rough.
"Debris was flying everywhere," Allison Lester said in an interview Friday with ABC's "Good Morning America."
Lester's boyfriend, Trent Behr, said they saw a woman in the water and helped to pull her into the boat. He said he was about to start CPR when an EMT arrived and took over.
A spokeswoman for Cox Medical Center Branson said four adults and three children arrived at the hospital shortly after the accident. Two adults were in critical condition, and the others were treated for minor injuries, Brandei Clifton said.
Stone County Sheriff Doug Rader said an off-duty deputy working security for the boat company helped rescue people after the boat turned over. Dive teams from several law enforcement agencies assisted in the effort.
Suzanne Smagala with Ripley Entertainment, which owns Ride the Ducks in Branson, said the company was assisting authorities. She said this was the ride's only accident in more than 40 years of operation.
In the hours after the accident, the lake was calm. But another round of thunderstorms passed within 10 miles of the area Friday morning, and more storms were forecast for later in the day, some severe, weather service meteorologist Jason Schaumann warned.
Weather can change rapidly in this part of the country, moving from sunshine and calm to dangerous storms within minutes, Schaumann said.
A severe thunderstorm warning had been issued for Branson at 6:32 p.m. Thursday, before the boat tipped over.
"Tornado warnings get a lot of publicity, and severe thunderstorm warnings should be taken very seriously too, particularly if you are in a vulnerable area like a lake or campground," he said.
Investigators from the National Transportation Safety Board were expected to arrive on the scene later Friday morning.
President Trump tweeted his condolences, extending his sympathies to the families and friends of those involved.
Branson, about 200 miles southeast of Kansas City, is a popular vacation spot, offering entertainment ranging from theme parks to live music.