In another revelation of safety lapses, Hokkaido Railway Co. says it operated a diesel-powered train for several runs on the Okhotsk express service between Sapporo and Abashiri with an onboard automatic brake effectively disabled.

JR Hokkaido said Monday that a valve cock that should have been opened to activate the emergency brake system had been shut. It added that the valve has to be manually closed, so it can’t be ruled out that the valve was closed intentionally.

With the valve shut, the automatic emergency brake would not work even if the automatic train stop or any of the two other safety systems were activated, according to the railway.

Makoto Toyota, a JR Hokkaido managing director, offered an apology at a news conference early Tuesday at the railroad’s headquarters in Sapporo. The revelation followed earlier announcements of failures to properly inspect tracks and other lapses.

Toyota said the latest problem was discovered through a routine quarterly inspection Monday and the carrier had yet to determine when the valve was closed. The train had traveled about 48,000 km after clearing an inspection July 12, when no abnormality was found.

The company conducted an emergency inspection on 245 trains of the same design but did not find any abnormalities, it said. The problem was reported to the Hokkaido District Transport Bureau of the Land, Infrastructure, Transport and Tourism Ministry.

One of the three safety systems, the automatic train stop system, alerts drivers and activates brakes whenever trains exceed the speed limit or fail to stop in response to a signal.

The railway said that when an alarm rang during the inspection, the emergency brake that should have simultaneously activated failed to do so. It was still possible to manually stop the train, it said.