The planned restart of four reactors in central and southwestern Japan will be delayed as nuclear operators need time to confirm whether peripheral equipment used parts affected by Kobe Steel’s data fabrication, the operators said Thursday.

The reactors affected are the Nos. 3 and 4 units at Kansai Electric Power Co.’s Oi plant in Fukui Prefecture and the Nos. 3 and 4 units at Kyushu Electric Power Co.’s Genkai plant in Saga Prefecture. All four reactors were originally set to go online early next year.

According to the Nuclear Regulation Authority, which received reports from utilities after the data fabrication came to light, Kobe Steel Ltd. products were used in the four reactors. But the utilities said at the time they were not products affected by the data fabrication.

Kansai Electric Power has so far ruled out any safety concerns, and on Monday Shigeki Iwane, the firm’s president, said he didn’t expect the issue would cause a delay.

But the company is now considering pushing back the schedule for restarting the Oi reactors in order to inspect their peripheral equipment, company officials said.

Just days earlier, Fukui Gov. Issei Nishikawa gave final local consent for the reactivation of the two reactors, which have cleared a set of new safety requirements introduced after the 2011 Fukushima nuclear crisis.

Fukui also hosts Kansai Electric Power’s Takahama plant, where two reactors have already resumed operation. There are lingering concerns over whether the utility and residents are fully prepared for the risk of a scenario involving simultaneous disasters at the two nearby complexes.

The Fukuoka-based Kyushu Electric said Thursday it will postpone the reactivation of the Genkai reactors to March and May, respectively. The firm has found that its reactor containment vessels used reinforcing bars supplied by Kobe Steel. But the products were made at factories that were not involved in data fabrication, according to the utility.

The reactivation of the four reactors at the Oi and Genkai plants would bring the number of reactors operating in Japan to nearly 10, depending on whether other currently idled reactors go online as well.

Japan currently has about 40 commercial reactors, but progress to bring them back online has been slow amid lingering safety concerns.

Kobe Steel has admitted to falsifying data for its products and specifications — including aluminum, copper, steel powder, liquid crystal display materials and special steel products — which were supplied to 525 companies, from major automakers to bullet train operators.