TAIPEI (AFP) — An explosion in a Taiwan department store on Thursday killed four people and left another “without vital signs,” authorities said, with videos showing large pieces of debris raining on the street.

Seven people were injured in the blast in the food court on the 12th floor of the Shin Kong Mitsukoshi department store in the city of Taichung, the National Fire Agency said.

The floor was believed to be closed for construction work at the time of the incident, the agency said.

Video posted on social media and verified by Agence France-Presse (AFP) showed the moment of the explosion, with cladding and other debris flying off the building and dust billowing from inside.

Liao Yu-fu, 26, told AFP he was woken from a nap by the sound of the explosion and thought it was a “plane hitting a house.”

“There was a vibration and even my bed was shaking,” said Liao, who can see the department store from his home.

“The sound lasted for a long time and I was scared.”

A woman, who had been on the sixth floor of the store at the time, said there was a “very loud vibration” and then debris began falling.

“At first, we thought it’s an earthquake,” the woman told local broadcaster TVBS.

“When I walked down the stairs, there was broken glass on every floor at the elevator entrance. Every floor is affected.”

Taichung Mayor Lu Shiow-yen told reporters she had been working in the city government building next to Shin Kong Mitsukoshi when she felt a “vibration” at around 11:30 a.m.

“The explosion is very serious and the rescue is ongoing,” Lu said.

The fire department dispatched 56 vehicles, 136 people, a dog and a drone to carry out search and rescue efforts, the National Fire Agency said.

It is not yet known what caused the blast.

The fire agency urged people to stay away from the disaster site.

Lu said the explosion had affected a wide area and at least one passerby was among the victims.

“There are many office buildings and homes in this area and we ask everyone to cooperate with the restrictions for your safety,” Lu said.

Video posted on social media showed what appeared to be large pieces of metal, cladding and debris scattered over the footpath outside the department store and nearby streets.

At least two people could be seen lying on the ground while another appeared to receive treatment from rescuers.

Another video showed extensive damage near a set of elevators inside the department store.