WASHINGTON — The House Ethics committee says it is continuing an investigation of Rep. John Conyers of Michigan, the longest-serving member of Congress and the top Democrat on the Judiciary Committee.

The independent Office of Congressional Ethics said in a report that there is substantial reason to believe that Conyers continued to pay his former chief of staff even after she was suspended following her guilty plea on a charge of receiving stolen property. Conyers is in his 27th term representing Detroit.

Conyers said in April 2016 that longtime staffer Cynthia Martin was placed on unpaid leave while he reviewed the matter. But the ethics office said Martin was paid more than $13,000 a month through August 2016. She was fired in October.

A spokeswoman said Conyers is cooperating with the inquiry.