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BRANSON, Mo. — Authorities say it could take several days to raise a duck boat that sank in southern Missouri, killing its driver and 16 passengers.

Missouri State Highway Patrol Sgt. Jason Pace says the vessel came to rest in 80 feet of water in the Lake of the Ozarks. Authorities initially said it would be raised Friday but Pace says it will take several days to get the equipment in place. He says investigators “want to preserve evidence as best is possible.”

Pace says the area has been secured and the investigation turned over to the National Transportation Safety Board and the Coast Guard.

Pace says divers indicated that the water visibility was better than normal, expediting the recovery of the victims’ bodies. They ranged in age from 1- to 70-years-old.

Missouri State Highway Patrol Sgt. Jason Pace said 14 people survived, including seven who were injured when the Ride the Ducks boat sank on Table Rock Lake in Branson Thursday evening.

Stone County Sheriff Doug Rader said late Thursday that stormy weather likely made the boat capsize.

The National Weather Service said thunderstorms brought winds of 50 to 65 mph to the Branson area Thursday evening. After a calm night on the lake, another round of thunderstorms passed within 10 miles  of the area before 7 a.m. Friday and more are forecast, 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 was 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.

Passengers on a nearby boat described the chaos as the winds picked up and the water became 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 the body of 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 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 an off-duty sheriff’s deputy working security for the boat company helped rescue people after the boat capsized. Dive teams from several law enforcement agencies assisted in the effort.

The National Transportation Safety Board investigators are expected to arrive on the scene Friday morning.

President Donald Trump tweeted his condolences Friday, extending his deepest sympathies to the families and friends of those involved.

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 only 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. An EF2 tornado that bounced through downtown Branson in 2012 destroyed dozens of buildings and injured about three dozen people, but killed no one.

Duck boats, which can travel on land and in water, have been involved in other deadly incidents 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 duck boat sank near Hot Springs, Arkansas.

Safety advocates have sought improvements since the Arkansas deaths. Critics argued that part of the problem is that too many agencies regulate the boats with varying safety requirements.

Duck boats were originally used by the U.S. military in World War II to transport troops and supplies, and later were modified for use as sightseeing vehicles.