NASHVILLE, Tenn. — The Tennessee Bureau of Investigation is probing the domestic violence arrest involving the husband of a top aide to Chattanooga Mayor Andy Berke.

Exactly what led to the alleged domestic incident is unclear, but it resulted in the mayor and the city’s police chief taking the unusual step of offering statements denying unspecified involvement with the aide.

The TBI said in a statement Friday that Hamilton County District Attorney Neal Pinkston asked it to investigate the arrest of the husband of mayoral aide Lacie Stone, but the agency declined to give more details.

According to the police report cited by several news outlets, Bobby and Lacie Stone had argued about her cellphone, which was crushed during the altercation.

An attorney for Bobby Stone did not respond to a message seeking comment.