TOKYO (AP) -- More than half of Toyota's shuttered assembly lines will start running again Tuesday, and carmakers Mazda and Honda plan to restart production as well, after a key parts supplier damaged by a major earthquake resumed operations Monday.

Factories of Toyota Motor Corp. and other major Japanese automakers have been shut because of a lack of parts following the damage to piston-ring maker Riken Corp.'s plant in Kashiwazaki, in north-central Japan, near the epicenter of the magnitude 6.8 earthquake on July 16.

Riken restarted production of some auto parts on Monday after workers replaced damaged equipment and restored the factory's gas and water supplies, a company spokeswoman said on condition of anonymity, citing protocol.

"We resumed production today, although there is a delay in some lines," Riken said in a statement. Production of key parts, including piston rings and seal rings, have nearly returned to normal, the company said.

Toyota said Monday 20 of its 31 auto assembly lines will be running by Tuesday, although later plans were still undecided.

Toyota's 12 factories in Japan have suspended operations since Thursday. The suspension has resulted in an output loss of about 46,000 vehicles, which may climb to about 55,000, Toyota President Katsuaki Watanabe told reporters.

Mazda Motor Corp., an affiliate of Ford Motor Corp., will start operations Monday evening at one of two factories in Japan, according to spokeswoman Aya Takahashi. The other factory will resume work Tuesday, she said. The company's output loss from the suspension is 4,500 vehicles, she said.

Honda Motor Co. also said Monday that two of its automobile plant and a motorcycle factory will resume production Tuesday. Two other auto production plants will remain closed, Honda said.

Nissan Motor Co. has halted some plants through Tuesday.

Mitsubishi Motors Corp. said Monday it expected to procure enough parts to reopen its domestic plants on Wednesday and Thursday. It was too early to say whether production would continue Friday, the automaker said in a statement.

Toyota shares fell 1.19 percent to 7,470 yen (US$62; ?45), Honda lost 1.98 percent to 4,460 yen (US $37; ?27), and Mazda dropped 1.97 percent to 695 yen (US$5.70; ?4.10).