Sanyo Electric has resumed chip production at a factory that automatically stopped when a powerful earthquake hit on Monday.

The factory in Ojiya, Niigata prefecture, was heavily damaged in 2004 when another powerful earthquake hit the same area but this time escaped without any serious problems. Operations at the plant, which makes semiconductor chips for various consumer electronics devices, resumed on Tuesday, Sanyo said.

At least nine people were killed and more than 1,000 people injured by Monday's quake, which occurred at 10:13 am local time. The magnitude 6.8 quake was centred about 17 kilometres underground just off the coast and registered in three locations an intensity of 6+ on Japan's scale of 0 to 7.

Hundreds of homes, most of them traditional Japanese houses made of wood, collapsed as a result, and around 12,000 people were evacuated to shelters. Rain has heightened the risk of landslides of soil weakened by Monday's quake.