Shikoku Railway Co. has neglected to repair around 50 bridges on its network even though irregularities were detected by regular checks more than three years ago, sources revealed.

The railway operator, better known as JR Shikoku, also failed to keep proper records of cracks, corrosion and other defects on some 1,100 bridges, representing more than 40 percent of all the bridges in its service area, the sources said Friday.

Some of the defects date back 23 years.

Although 100 of the bridges were found to rapidly require maintenance, half of them have been waiting for repairs for over three years, according to the sources.

The Board of Audit discovered the irregularities while examining the results of JR Shikoku’s regular checks of roughly 2,600 bridges in fiscal 2012. The board is set to urge JR Shikoku to swiftly work out and implement measures to fix the defects and to start maintaining proper inspection records.

JR Shikoku said it did not carry out repairs because it believed the irregularities didn’t threaten to disrupt services. But following the board’s findings, the company said it will examine steps to quickly rectify the situation.

JR Shikoku conducts regular bridge checks every other year based on a transport ministry ordinance and, if abnormalities are found, it is required to quickly repair them. The company is subject to the board’s examination because a government-linked entity holds its shares.

The findings follow revelations last week that Hokkaido Railway Co., also part of the Japan Railway group, had failed to repair numerous rail defects on its network.