SEOUL, South Korea (AP) — South Korean rescue workers on Saturday recovered the remains of 10 people from the charred wreckage of an auto parts factory in the central city of Daejeon, where a blaze likely triggered by an explosion injured at least 59 others and left four missing.

The Ministry of the Interior and Safety said 25 people were seriously injured but officials didn’t immediately confirm whether any were in life-threatening condition. More than 500 firefighters, police and emergency personnel were deployed to contain the fire and conduct rescue operations after the fire broke out Friday afternoon.

Videos and photos from the scene showed thick gray smoke billowing from the complex and some workers jumping from a building.

Nam Deuk-woo, fire chief of the city’s Daedeok district, said the blaze destroyed a factory building that firefighters initially could not enter over fears it might collapse. Searches for the missing workers began late Friday after officials deployed unmanned firefighting robots to cool the structure and conducted a safety inspection.

The remains of one person were found on the second floor of the building, while nine others were discovered in what is believed to have been a gym on the third floor, Nam said. He said rescuers had searched all accessible areas as of Saturday morning, and that the remaining four were likely trapped beneath collapsed rubble. Further safety inspections were planned before crews attempt to remove the debris and search for the missing workers.

Nam said police have identified one of the workers who died, while genetic testing was being conducted on the other nine.

The fire was reported at about 1:18 p.m. Friday. Nam said the cause was not immediately known, but the blaze appeared to have spread rapidly, with witnesses reporting an explosion. Firefighters focused on preventing the blaze from spreading to an adjacent facility and isolating explosive chemicals. Nam said workers recovered more than 100 kilograms (220 pounds) of highly reactive chemicals from the site.

Some people were injured when they jumped from the building to escape, while others suffered from smoke inhalation, officials said. As of Saturday morning, 28 people were hospitalized and four of them underwent surgeries for broken bones and other injuries.

About 120 vehicles and pieces of equipment, including aircraft, an unmanned water cannon vehicle and two firefighting robots for hard-to-reach areas, were deployed along with hundreds of personnel.

South Korean President Lee Jae Myung called for the full mobilization of personnel and equipment to contain the fire and support rescue operations.