The infrastructure ministry has urged Toyo Tire & Rubber Co. to report by the end of this month the findings of checks on substandard quake-absorbing building materials sold by a subsidiary, transport minister Akihiro Ota said Tuesday.

Buildings where the materials were used include hospitals and fire department facilities.

The ministry was expected to conduct on-site inspections at Toyo Tire's Akashi factory in Hyogo Prefecture later in the day, after it emerged the subsidiary manufactured and sold seismic isolation rubber that doesn't meet government standards.

"It is extremely regrettable that the misconduct has been found," Ota told a news conference. "This damages trust in Japanese technical standards, and it is unforgivable."

Ota said the ministry has urged Toyo Tire to speed up its safety checks. Whereas it currently expects to take one month, the ministry needs a report on the outcome by the end of March.

So far, 55 buildings have been found to have substandard movement-absorbing equipment sold by the subsidiary of Toyo Tire. The ministry on Tuesday named 15 of them because they are public buildings: