An explosion Saturday at a chemical plant in Ojima, Gunma Prefecture, killed four people and injured at least 27 — many by flying shards of glass, officials said.

The blast took place at 6 p.m., gutting the plant, operated by Tokyo-based Nisshin Chemical Co., damaging scores of buildings and breaking the windows of nearby shops and cars.

“We are currently investigating the cause of the explosion, but it damaged several buildings within a 300-meter radius of the factory,” a fire official said.

The official added that some three hours after the blast, smoke was still billowing from the facility and 30 emergency vehicles were on the scene.

The official said the explosion damaged 200 nearby homes and knocked out power. Roads in the area were also closed, and residents were being evacuated.

Two of the people killed were workers inside the plant at the time of the explosion, the Kyodo News agency reported.

“I heard a tremendous sound, and five or six windows were broken at my home. I can still see red flames rising into the air,” said Katsuyuki Kato, an Ojima resident who lives about 1 km from the plant, in a statement to Kyodo News.