The Kashiwazaki nuclear power could be closed for a year
There are fears of power shortages in Tokyo, as the scale of the earthquake damage to the country's biggest nuclear power station becomes clear.
The government reportedly wants the Kashiwazaki plant to stay closed for more than a year for safety checks.
Kashiwazaki contributes about 12% of the Tokyo Electric Power Company's supplies to the capital.
Tepco was criticised after revealing that Monday's quake caused more than 50 malfunctions at its Niigata plant.
Tepco is considering restarting six mothballed thermal power plants to meet demand over the summer.
The company has also asked six other Japanese power companies to sell it emergency electricity until the end of September.
"We are working hard to prevent the worse case scenario, an energy shortage," Shogo Fukuda, Tepco spokesman, was quoted by the Associated Press as saying.
"We would also call on our customers to redouble their energy-saving efforts."
Tepco did not say when Kashiwazaki might re-open. The safety checks alone are expected to take until the end of August.
But the Nikkei newspaper reported on Thursday that the government could order the plant to be closed for as long as a year.
Impact on automakers
On Wednesday, Tepco admitted that 50% more radiation was discharged into the sea than had initially been reported, although this remains well below danger levels.
The reported number of barrels containing low-level nuclear waste that tipped over at the plant was increased from 100 to 400, with the lids knocked off 40 of them.
The malfunctions and the subsequent revelation that a fault line could stretch directly under the plant have triggered renewed concern in Japan about the safety of its nuclear industry.
Most nuclear power stations in Japan are built to similar specifications as the plant in Niigata, says the BBC's Chris Hogg in Tokyo.
There are fears that they too could be damaged if they were hit by an earthquake of similar intensity.
A minister has asked power companies to check as soon as possible whether all their nuclear facilities can withstand strong tremors, but the power companies have told them that could take three years, our correspondent adds.
Monday's earthquake left 10 people dead. Hundreds more were injured and scores of homes have been flattened.
The earthquake has also affected Japan's automakers.
The temporary closure of a factory in Kashiwazaki belonging to key supplier Riken Corp - a maker of transmission and engine parts - will force top manufacturers such as Toyota and Nissan to scale back production.
Toyota is to stop production lines at its plants in Aichi on Thursday and Friday, and review the situation on Monday, the Associated Press news agency quoted a spokesman as saying.