A Japanese toilet-maker has offered free repairs to 180,000 of its customers after a wiring problem caused some of its high-tech WCs to start smoking and even burst into flames.

Toto Ltd, the country's biggest toilet-maker, said three of its Z-series combined bidet-toilet units have caught fire in the past year because of faulty wiring. A further 26 units have sent up smoke.

"Fortunately, nobody was using the toilets when the fire broke out and there were no injuries," Erni Tanaka, a Toto spokeswoman, said. "The fire would have been just under your buttocks."

Japan is renowed for its high-tech toilets, pioneered by Toto, which routinely baffle foreign visitors. The popular Z series features a pulsating massage spray, a power dryer, built-in deodorising filters and lids that open and close automatically.

The company has also released models that make flushing sounds to mask its customer's bodily functions and others that include stereo units and emit fragrances.

The models affected by the wiring fault were manufactured between May 1996 and December 2001. They were not sold overseas.

“We apologise deeply for the trouble we have caused to our customers,” the company said in a statement.

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