Mitsubishi Motors Corp. submitted false reports to transport authorities on defective wheel hubs just five months after an outside advisory panel had told the company its business practices were improving, industry sources said Monday.

The panel was set up by Mitsubishi Motors in September 2000, following revelations the preceding summer the company had systematically concealed customer complaints that would have compelled it to carry out recalls, the sources said.

The seven-member panel, which included a lawyer who once served as a Supreme Court justice and an automobile industry critic, wound up its activities in August 2001, issuing a report stating that the company’s corporate culture had improved steadily.

The panel met 12 times — with the final meeting held at the end of August 2001 — and examined measures undertaken by the automaker to improve quality control.

One of the measures, compiled by an in-house committee, was the placing of sequential serial numbers on all documents to prevent concealment of information regarding customer complaints, the sources said.

But in January 2002, when a fatal accident involving a large Mitsubishi truck took place in Yokohama, the automaker filed false reports with the Transport Ministry regarding the vehicle’s wheel hubs.