An explosion and fire at a Hanwha Aerospace plant in Daejeon killed five workers and injured two others, authorities said Monday.

Under the Serious Accidents Punishment Act, executives of the company could face penalties if the explosion is found to be the result of safety failures.

Police and fire authorities said the explosion occurred at 10:59 a.m. About 100 firefighters, along with dozens of vehicles and other firefighting equipment, were dispatched to the scene, bringing the blaze under control about 50 minutes after it broke out and fully extinguishing it at 1:07 p.m.

The seven workers were conducting cleaning operations to remove explosive residue from tools used in the manufacturing process of rocket propellant, according to a Hanwha Aerospace executive.

The plant is the company's key facility producing equipment for the aviation, defense and space industries.

The five victims died at the scene, where a blaze also broke out, while the two injured workers managed to escape on their own.

One of them suffered severe burns over most of their body and remained hospitalized, while the other sustained minor injuries and was treated before being discharged.

The bodies of the dead victims were severely damaged, making immediate identification difficult, according to authorities.

Investigators plan to examine the cause of the explosion after securing building plans and other information from the factory, which is classified as a restricted national security site.

The accident was the latest in a series of deadly explosions at the Daejeon plant of Hanwha Aerospace, a defense arm of Hanwha Group.

In May 2018, a blast killed five workers, while another explosion and fire in a propellant-processing laboratory killed three workers in February 2019.

The executive explained that the company had invested heavily to automate and streamline relevant processes following the accidents in 2018 and 2019, but that the process involved in Monday's accident was "one that we had not considered to pose a significant safety risk."

Senior executives of the company may face investigation over alleged violation of the Serious Accidents Punishment Act, which dictates criminal liability for CEOs and executives in the event of one or more deaths, or two or more injuries requiring over six months of treatment.

Hanwha Group and Hanwha Aerospace expressed their deepest condolences to the victims and their families and pledged full cooperation with authorities investigating the accident.

“We are devastated and deeply saddened by the loss of five valued employees in the accident. We offer deep condolences to the bereaved families," group Chairman Kim Seung-youn said in a statement issued by the company.

He ordered company officials to pay their respects to the victims and spare no effort in providing all necessary support and medical care, the statement read.

The companies added that they “will do everything possible to respond to and manage the aftermath of the accident,” noting that a group-wide task force team will be set up to work closely with authorities to handle the situation.

President Lee Jae Myung ordered authorities to mobilize all available resources for rescue and recovery efforts, Cheong Wa Dae spokesperson Kang Yu-jung said in a written briefing.

“The president instructed authorities to conduct a thorough investigation into the cause of the accident and prepare measures to prevent similar accidents,” Kang wrote.

Prime Minister Kim Min-seok visited the site and instructed authorities to fully support rescue efforts and prevent further damage, directing central and local government bodies — including the Ministry of the Interior and Safety, the National Fire Agency, the National Police Agency and the Daejeon city government — to coordinate their response.

Kim called on authorties to thoroughly review all remaining issues, ensure that bereaved families receive full support.

Minister of Employment and Labor Kim Young-hoon also visited the scene and called for a thorough investigation into the root causes of the accident, including the cause of the explosion and the state of safety management at the facility. He ordered a swift and rigorous inspection into any potential violations of occupational safety and health laws.

Defense Minister Ahn Gyu-back wrote on social media that his ministry, together with the Defense Acquisition Program Administration, would "provide full technical support for the investigation into the cause of the accident."

"We will also actively cooperate in establishing stronger safety measures for defense industry workers to ensure that such a tragedy never happens again," he added.