OSAKA, Feb. 1 (Xinhua) -- About 5,000 criminal cases were neglected over years as evidence and files on the cases were abandoned in police stations of Japan's Osaka prefecture, local media reported on Monday.

Boxes filled with files and evidence from investigations were found abandoned in heating rooms and storage space instead of being sent to prosecutors at 61 of the 65 police stations in Osaka Prefecture. Some of the files are dated as far back as 30 years ago.

The statute of limitations for about 4,300 of the 5,000 cases had already expired when the files and evidence were found. In about 1,000 of the expired cases, suspects had nearly been identified.

Most of the cases involved assault and embezzlement rather than murders or other serious crimes, and were neglected as they were not "high-priority cases", according to the police.

The number of improperly stored files might rise further as the police are still compiling their findings.