At least 20 steel plants have been identified for investigation over the alleged sale and distribution of substandard and radioactive steel, National Bureau of Investigation (NBI) Director Melvin Matibag said Tuesday.

Matibag said the facilities were identified through efforts by the NBI, Presidential Anti-Organized Crime Commission (PAOCC) and other law enforcement agencies.

He said the investigation would not be limited to Davao and would expand to other parts of the country.

Authorities previously raided Davao Mighty Steel Corp. over allegations that it was selling and distributing substandard steel.

Matibag alleged that 70 percent of structures damaged during an earthquake in General Santos City and Sarangani had used steel traced to the facility.

Authorities also rescued 174 Filipino workers during the raid.

A total of 194 factory personnel were examined, 57 of whom had documented medical findings, while two tested positive during radioactivity scanning, according to authorities.

Matibag urged consumers, builders and government contractors to verify whether the steel they purchase complies with required standards and to scrutinize their suppliers.

He also appealed to the public not to politicize the government's operations against steel manufacturers.

“Our appeal is for people to understand that this is not about political preference, this is not about which region, and this is not about business,” Matibag said.

“This is about the NBI and PAOCC doing their jobs as law enforcement agencies to ensure that our fellow Filipinos are protected,” he added.