SEOUL, South Korea — South Korea plans to halt operations at two nuclear reactors and delay the start of operations at another after discovering that the facilities were using components whose safety certificates were faked.

The Shin-Kori No. 2 reactor and Shin-Wolsong No. 1 reactor will be shut down for about four months to replace control cables supplied under fake quality warranties, South Korea’s energy ministry said in a statement Tuesday.

The government also ordered the replacement of cables at the Shin-Kori No. 1 reactor, which is shut down for regular maintenance, and at the new Shin- Wolsong No. 2 reactor, which is in review before commencing operations.

South Korea, which depends on nuclear energy for more than 30 percent of its electricity, may face “unprecedented” power shortages during the summer season because of the shutdowns, Vice Minister for Energy Han Jin Hyun told reporters.

Tuesday’s decision will mean 10 of South Korea’s 23 reactors are offline, according to Korea Hydro & Nuclear Power Co., which operates the reactors.

“Other fuel sources, mostly gas, will have to be used to make up for lost supply,” Lee Chang Mok, a utilities analyst at Seoul-based Woori Investment & Securities Co., said by phone. “Efforts to conserve electricity should follow, and a drive to rein in demand could provide the rationale for power tariff increases.”

South Korea’s nuclear regulator began its investigation in April following information from a whistle-blower, according to the energy ministry statement.

An earlier investigation into faked certificates led to the suspension of two reactors in November. Korea Hydro Chief Executive Officer Kim Kyun Seop said at the time he would resign once the “mess” surrounding the certificates was fixed.