A remote-working employee of the world's biggest nuclear power plant left important documents on the roof of his car before driving off. It could delay a Tepco plant restart.

• A Tepco nuclear plant employee in Japan left work documents on the roof of his car before driving off.
• The employee had brought the documents home as he was working remotely.

A remotely working employee at the world's largest nuclear power plant could complicate the restart of the facility, which has been offline since 2012.

A staffer at Japan's Tokyo Electric Power, or Tepco, left work documents on top of his car — before driving off and losing them, according to Insider's translation of the company's statement on Monday.

Tepco said it found out about the incident the following day when residents turned up at the company's office with pages of documents from the Kashiwazaki-Kariwa nuclear power plant in Japan's Niigata prefecture, located on the country's west coast.

The documents were related to flood and fire protection at the plant, according to the company.

Tepco said while the employee lost 80 pages of documents, the company was still trying to 38 pages.

Following the incident, warnings were issued to both, the employee and their manager, the company said.

But the incident could thwart efforts to restart the Kashiwazaki-Kariwa nuclear power plant, which had been offline since 2012 amid strict nuclear energy regulations and safety lapses following the Fukushima nuclear disaster in 2011, per Bloomberg.

The Fukushima disaster was the second worst nuclear accident in the history of nuclear power generation after Chernobyl in the former Soviet Union in 1986.

Just last week, Japan's Nuclear Regulation Authority decided to keep a de facto ban on the Kashiwazaki-Kariwa facility, according to various media reports, including broadcaster NHK.

The regulator said Tepco has not fully improved security measures at the plant, per the broadcaster.

Tepco did not immediately respond to Insider's request for comment.