TOKYO (AP) _ A key Japanese auto parts supplier partially resumed operation Monday, a week after a major earthquake ravaged its production line but top carmaker Toyota said it will keep its own production on hold at least another day.

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

Riken restarted production of some auto parts 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.

Plant workers are currently monitoring the operation, the spokeswoman said. Riken plans to release details of the production later Monday, she said.

Toyota's 12 factories in Japan have suspended operations since Thursday.

The renewed production at Riken is not yet enough for the automaker to restart operations and the company has not yet decided whether it would be possible to resume Tuesday, a company spokesman said on customary condition of anonymity.

The suspension has resulted in an output loss of about 46,000 vehicles, the spokesman said.

Honda Motor Corp., Mitsubishi motors Corp. and Mazda Motor Corp. have already said they plan to halt most operations through Monday.

Nissan Motor Co., whose operation has been halted at some plants, will continue the stoppage through Tuesday.