Despite irregularities found last year in subway trains operated by the Tokyo Metropolitan Government, officials kept the trains in service and "saw no need" to report the irregularities to the Transport Ministry, officials admitted Tuesday.

Passengers reported abnormal shaking in a subway car and officials discovered long gashes left on the tracks of Tokyo's No. 12 subway line during the evening rush hour in October 1998. Seven months later -- on the same line -- train operators discovered that a connecting platform between cars was askew at Shinjuku Station.

In both cases, officials decided to continue operations between Shinjuku and Hikarigaoka Stations with passengers aboard "due to 'scheduling considerations,' " before taking the train in for maintenance checks.

Inspections after the first incident revealed multiple cracks, some as much as 20 cm long and 3 cm wide, in the base of the bogies on the train as well as on eight other trains. Poor repair welding following the first incident caused the cracks to open up in 33 of the 44 previously welded locations, leading to the second incident, officials said.

"It is unlikely, but in an extreme case the cracks might have opened up and caused a derailment," admitted Akio Mizumoto, an official of Tokyo's Bureau of Transportation. "But those on site decided that the irregularities posed no danger."

In both cases, metropolitan government officials decided not to report the irregularities to either the Tokyo governor or the Transport Ministry because the problems did not cause schedule delays or injuries and does not fit the Transport Ministry's criteria for accidents.

The cracks have since been rewelded and reinforced, officials said.

"A terrible accident might have happened," said Yasunobu Watanabe, of the Japanese Communist Party, speaking before a special budget committee.

The revelation came less than a week after a Hibiya Subway accident claimed the lives of five people.

Asked whether officials decided to report the irregularities after the Hibiya Line accident, Mizumoto said, "We didn't report it initially; it would have been strange to suddenly report it then."

"This happened during my term, and I am also responsible," Tokyo Gov. Shintaro Ishihara said. "This is something that should of course have been reported."