New Orleans on Friday was reportedly targeted by a cyberattack that struck several computers in the city hall, authorities said. A spokesman for Mayor LaToya Cantrell said the attack started sometime after 11 a.m. and while the extent of the attack is still unknown, city personnel—including police and firefighters—were advised to “power off all computers and shutdown cellphones,” in announcement over the loudspeaker in City Hall.

“The City of New Orleans is under a cyber attack. Please power off your computers and unplug them immediately. Await further instructions,” an internal text message from the New Orleans Office of Homeland Security and Emergency Preparedness said. The attack, however, has not affected the New Orleans Police Department 911 emergency system, a police spokesperson said.