Missouri, US.- The country-and-western tourist town of Branson, Missouri, mourned Friday for more than a dozen sightseers who were killed when a duck boat capsized and sank in stormy weather in the deadliest such accident in almost two decades.

Divers found four more bodies in Table Rock Lake, bringing the death toll to 17, including the crew member who was driving the amphibious boat. In their initial assessment, authorities blamed thunderstorms and winds that approached hurricane strength, and a full investigation was underway.

“Branson is a city full of smiles,” Mayor Karen Best said. “We have so much fun here. But today we are grieving and crying.”

The risk of heavy weather was apparent hours before the boat left shore.

The weather service station in Springfield, about 40 miles (64 kilometers) north of Branson, issued a severe thunderstorm watch for its immediate area Thursday, saying conditions were ripe for winds of 70 mph. It followed up at 6:32 p.m. with a severe thunderstorm warning for three counties that included Branson and the lake. The warning mentioned both locations. The boat went down about 40 minutes later, shortly after 7 p.m.

“When we issue a warning, it means take action,” meteorologist Kelsey Angle said. Suzanne Smagala with Ripley Entertainment, which owns Ride the Ducks in Branson, said the company was assisting authorities. She said this was the company’s only accident in more than 40 years of operation.

The boat was carrying 29 passengers and two crew members on a pleasure cruise, and everyone aboard had been accounted for by midday Friday. Seven of the 14 survivors were hurt when the vessel went down. At least two were hospitalized in critical condition. The captain survived, authorities said.

Brayden Malaske, of Harrah, Oklahoma, was on vacation with family when he boarded a replica 19th-century paddle wheeler known as the Branson Belle on the same lake just before the storm hit.

At the time, he said, the lake seemed calm, and no one was worried about the weather.

“But it suddenly got very dark,” he recalled. In a short video taken by Malaske from a dock, the duck boat can be seen wallowing through the choppy, wind-whipped lake, with water only inches from its windows. Dark, rolling waves crash over its front end. The footage ends before the boat capsizes.

Later, people on Malaske’s boat saw a duck boat passenger “hanging on for dear life” to the paddle wheel of the Belle, he said.

The mayor identified the crew member driving the boat as Bob Williams, known informally as “Captain Bob.”

“He was at a great ambassador for Branson,” Best said. “He was at every event. He knew everyone. He was always promoting Branson.”

Authorities had not publicly identified the dead but said they included a 1-year-old child.

Named for their ability to travel on land and in water, duck boats have been involved in other serious accidents in the past, including the deaths of more than 40 people since 1999.

Five college students were killed in 2015 in Seattle when a duck boat collided with a bus. Thirteen people died in 1999 when a boat sank near Hot Springs, Arkansas.

“Duck boats are death traps,” said Andrew Duffy, an attorney whose Philadelphia law firm handled litigation related to two fatal duck boat accidents there. “They’re not fit for water or land because they are half car and half boat.”

Safety advocates have sought improvements and complained that too many agencies regulate the boats with varying safety requirements.

The boats were originally designed for the military, specifically to transport troops and supplies in World War II. They were later modified for use as sightseeing vehicles.

Passengers on a nearby boat described the chaos on the lake 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.

Stone County Sheriff Doug Rader urged anyone with video or photos of the accident to contact authorities.