Chicago's 911 system went down overnight when the city's state-of-the-art response system inexplicably crashed Monday evening.

Delores Robinson, a spokesperson for the city's Office of Emergency Management and Communications, told WLS that the system went down around 9 p.m. Monday and was back up by 1 a.m. Tuesday.

The department does not know what caused the system, which routes emergency calls to police officers in the field from the dispatch center at 1411 W. Madison St., to crash, CBS Chicago reports, but technicians were investigating and making repairs Tuesday morning.

Dispatchers communicated with police officers via radio, preventing the service interruption from causing any delays in response time, Robinson told the Chicago Sun-Times. The system has crashed before, but Robinson couldn't tell the newspaper when the most recent failure occurred.

Flickr photo by Highways Agency.

Related on HuffPost: