A city official says transit agency employees are suspected sabotaging safety devices on train doors. ``This appears to be an insider problem, someone who obviously knows enough about cars to disable them,'' said Frank Wilson, the Chicago Transit Authority's senior deputy executive director in charge of maintenance. Inspectors at a rail yard discovered the vandalism, involving the air-filled rubber edges that prevent doors from closing on passengers, Wilson said. Over the weekend, 25 doors on 18 cars were vandalized, he said. Air hoses either were disconnected or cut cleanly where they connect to a compressor, Wilson said Monday. On Tuesday, crews found 11 new cases of apparent tampering, including five instances of damage to cars that had been repaired since the weekend, he said. There were no passenger injuries linked to the faulty doors. Wilson has been very outspoken about the agency's problems since coming to Chicago a month ago from a similar post in Philadelphia. Last fall, the transit authority suspected employee sabotage when fuses necessary for emergency brake systems were missing in 100 cars. An investigation failed to produce any suspects.