Another seven people were injured in the blast in the food court on the 12th floor of the Shin Kong Mitsukoshi department store in the central west city of Taichung, the national fire agency said.

The area 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 AFP showed the moment of the explosion, with cladding and other debris flying off the building and dust billowing from inside.

“I was working in the city government building around 11.30am and because it’s right next to Shin Kong Mitsukoshi department store, I felt a vibration,” Taichung mayor Lu Shiow-yen told reporters.

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

The local fire department dispatched 56 vehicles and 136 people to carry out search and rescue efforts, the national fire agency said.

It is not yet known what caused the blast.

“The cause is subject to follow-up investigation and we call on the public to avoid going to the vicinity of the disaster site,” the national fire agency said.

Lu said the explosion had affected a wide area and at least one passer-by 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 can be seen lying on the ground and another apparently receiving treatment from rescuers.

Another video showed extensive damage inside the department store.