TAIPEI, Taiwan - A fire at a golf ball factory in Taiwan killed at least six people, three of them firefighters who died in an explosion, authorities said Saturday.

The fire, which began Friday evening and raged all night, injured more than 100 people, most of them workers, the Pingtung county government told local media.

One firefighter and three other people are missing.

Taiwan's President Tsai Ing-wen visited the scene on Saturday morning and expressed condolences to the victims' families. She said an investigation into the cause of the tragedy is underway.

"I want to thank everyone for their hard work and please stay safe," Tsai told emergency response personnel.

She also stopped at the morgue to pay respects to the victims and visited the injured at a hospital.

An official with the Pingtung Fire Department told local media that chemical peroxide stored inside the factory could have been the cause of the one large and several smaller explosions.

Several people were trapped inside due to the blasts, which caused a section of the factory roof to collapse.