Hokkaido Railway Co. said Sunday that a failure to perform track repairs quickly enough could have caused the derailment of a cargo train last week and that it has since uncovered another 97 cases of poor track maintenance.
An investigation carried out by the railway has found that the track width at the site of Thursday's derailment was beyond the safety limit. It has also led to the discovery of more unrepaired tracks, JR Hokkaido President Makoto Nojima said at a news conference in Sapporo.
"We are truly sorry for causing this," he said while ruling out the possibility of resigning over the fiasco.
In-house rules stipulate that a deviation of 19 mm or more must be rectified within 15 days of discovery. But the decision to make such repairs is usually left to employees on the scene, and the railway's headquarters might have little knowledge about the true condition of its tracks.
At the accident site, the track width was 20 mm wider than normal last October and 25 mm wider in June. JR Hokkaido said the areas in question had all been repaired by Saturday. The widest deviation confirmed was 28 mm, it said.
JR Hokkaido has been hit by a spate of recent accidents including three train fires between April and July. Another cargo train derailment last month has been blamed on heavy rain that swept away ballast and soil buttressing the railway ties.