Scuba divers are still searching for more than a dozen missing people after a crowded tourist boat carrying about 160 passengers sank Sunday afternoon in a reservoir near Medellin, Colombia. At least seven people are dead

Rescue teams pulled the body of a woman from the water Monday morning after suspending the search late Sunday night due to a lightning storm. At least 13 people are still missing about a day after the multistory ferry crammed with passengers visiting the popular holiday spot dramatically plunged into the water.

Three people are still in the hospital, Margarita Moncada, the head of the disaster response agency in Antioquia state, said Monday.

Shocking videos of the incident show the ferry, named El Almirante, rocking and submerging into the water as passengers scramble to the top floor. An armada of jet skis and recreational boats then surround the boat to help rescue passengers onboard.

It is not clear what caused the boat to suddenly sink. The ferry was the only vessel involved in the accident and sank in one of the deepest sectors of the reservoir, Moncada said in a press conference on Monday.

“Nobody really knows what happened,” said President Juan Manuel Santos, who had traveled to Guatape shortly after the accident to monitor rescue efforts. Naval officials are now investigating, along with Colombia’s Ministry of Transportation.

Survivors told local media that the boat seemed to be overloaded, and that many of the passengers had not been wearing life vests, however Santos said it was well below capacity. To make matters more complicated, the boat did not have a passenger list.

“It sank extremely quickly. It all happened in a few minutes,” said Luis Bernardo Morales, a fire service captain helping coordinate the rescue operation.

“What we have seen in the videos is that the boat was very close to the port,” Morales said, “and we do not know whether it was a mechanical failure, an overloading, or something to do with the currents that caused it to sink.”

“I reiterate the firm decision of the National Government and the authorities to carry out the strictest investigation of what happened in Guatapé,” Jorge Eduardo Rojas, Colombia’s minister of transportation, tweeted Monday.

His agency said that the company that owned the ferry had had authorization to run the boat, and 12 others, since 2009. It renewed its permission to operate in December and that it had “all its papers in order.”

Gonzalo Reyes, a musician who was onboard the boat, told Colombia’s Blu Radio that he was singing on the third floor when he heard a loud bang and the boat turned to the left side.

“That boat was not distributed to accommodate so many people,” Reyes told the news station. “I think there was overcrowding.” He also noted that members of the crew had not been wearing life vests.

This is a developing story. Follow BuzzFeed News on Twitter for updates.