Toyota, Honda and Mazda resumed production Tuesday at their domestic factories after key parts supplier Riken, damaged by last week's quake, resumed operations.

Factories of Toyota Motor Corp. and other major automakers had been shut because of a lack of parts following the damage to piston-ring maker Riken Corp.'s plant in Kashiwazaki, Niigata Prefecture, near the epicenter of the magnitude-6.8 quake.

Riken restarted production of some auto parts Monday after workers replaced damaged equipment and restored the factory's gas and water supplies.

Honda Motor Co. resumed production at an automobile plant and a motorcycle factory Tuesday, and a second auto plant was set to go back online later in the day, a company spokeswoman said on condition of anonymity, citing protocol. Two other auto production plants will remain closed for the time being, she said.

Mazda Motor Corp., an affiliate of Ford Motor Co., started operations at the second of two closed factories Tuesday after reopening the other the previous night, company spokeswoman Yukari Hara said. The company estimates its output loss from the suspension at 4,500 vehicles.

Toyota resumed production on 20 of its 31 auto assembly lines at its dozen factories, company spokesman Kazuaki Nakao said. The company said it will resume operations at all of its plants Wednesday.

All Toyota factories had suspended operations since Thursday. The suspension has resulted in an output loss of about 46,000 vehicles, which may climb to about 55,000, President Katsuaki Watanabe said Monday.

Nissan Motor Co. will restart production at all closed plants Wednesday, company spokeswoman Tomo Nagami said. The company estimates its output loss at about 12,000 vehicles, which it hopes to make up for through overtime work and stepped-up production, she said.

Mitsubishi Motors Corp. planned to resume production at three factories for two days starting Wednesday, the company said in a statement. Later plans will be decided based on the progress of Riken's recovery, it said.