State prosecutors on Wednesday raided some 30 companies that are suspected of having been involved in the provision of substandard reactor parts by falsifying quality warranties.

The raid was made as part of the prosecution probe into a corruption scandal late last year in which more than 13,000 substandard parts were supplied to nuclear reactors under fake warranties over the past 10 years. The government had to stop six reactors after they were found to be using parts with fake warranties.

"We've targeted and simultaneously raided 30 businesses which are greatly suspected of having forged warranties," a prosecutor said.

The prosecution do not believe the parts the businesses provided were core parts, but launched their probe in order to root out widespread irregularities in the nuclear power industry, the prosecutor said.

South Korea operates 23 reactors, supplying about 30 percent of its total electricity consumption. (Yonhap News)