Gloucester Mayor Sefatia Romeo Theken has hired two outside firms to conduct an “audit into the professional conduct’’ of Police Chief Leonard Campanello and a second officer, Detective Sergeant Sean Conners, who were put on paid administrative leave.

In a statement, the mayor announced the hiring of lawyer Thomas A. Mullen of Lynnfield to “perform an audit into the professional conduct’’ of Campanello, whom the mayor placed on leave with pay on Sept. 13, a move she made without offering a detailed explanation for her action.

The mayor also hired APD Management of Tewksbury to review Conners’s “professional conduct’’ while on the force. He was put on paid administrative leave Sept. 8 by the mayor, who did not disclose a reason for that action either.

Campanello has gained a national following as the architect of a police strategy that steers substance abusers to treatment instead of prison. He championed the idea in the North Shore city, and then with philanthropist John Rosenthal created the Police Assisted Addiction Recovery Initiative.

Campanello has insisted he did nothing wrong while chief nor at the nonprofit. However, he has stepped aside from the nonprofit while the city conducts its inquiry.

In the statement, the mayor wrote that the inquiry by Mullen and ADP is independent of any internal review by the city agencies — and is independent of her office, too.

“Both firms are operating independently of any city department, including the mayor’s office,’’ Romeo Theken said in the statement. “It is a priority for the city and administration to provide the residents of Gloucester external and objective audits and to uphold the standards expected by the mayor for all public roles.’’

There is no deadline for the inquiries, the mayor’s office said.

Terrence Kennedy, Campanello’s attorney, could not immediately be reached for comment.

John R. Ellement can be reached at ellement@globe.com. Follow him on Twitter @JREbosglobe.