SEOUL, South Korea (AP) — A 60-meter (196-foot) tower collapsed during demolition work at a decommissioned thermal power plant in the South Korean city of Ulsan, killing at least one person and leaving six others trapped under the rubble, officials said Friday.

Rescuers located one of the trapped people, who is feared dead, but have been unable to remove the person from the rubble. Two others were pulled to safety shortly after responding to the collapse on Thursday afternoon.

Another worker, who was rescued later, was pronounced dead at a hospital early Friday, said Kim Jeong-shik, an official with Ulsan's fire department.

Kim said the search for the remaining people was suspended Friday morning due to concerns over unstable rubble and will resume after stabilization work.

"We have deployed rescue dogs and they're conducting searches now. We also have a lot of detection equipment on site, including thermal cameras and endoscopes," Kim said in a briefing.

Officials said earlier that the first two people rescued escaped life-threatening injuries. More than 340 rescue workers and around 90 vehicles and equipment had been deployed to the site for search and rescue efforts.

Following the collapse, South Korean President Lee Jae Myung instructed officials to mobilize all available personnel and equipment for the rescue effort while ensuring the safety of rescue workers operating in the rubble.

The plant was decommissioned in 2021 after 40 years of operation. Officials said the boiler tower — one of three at the site — had been weakened as it was being prepared for demolition.