BOSTON — The 911 system across Massachusetts went down Tuesday afternoon, making it impossible for anyone to reach emergency services.

“The State 911 Department is aware of a disruption to the 911 system and is investigating the cause,” the state’s Office of Public Safety and Security said in a statement.

Dozens of communities reported the outage, but its cause was unclear.

Boston Police Commissioner Michael Cox advised the public to contact local police departments if they need help.

“In addition, if you’re having any issues that are medical related, or EMS or fire-related, you can go and pull your local call box, that’s the red light boxes that fire departments have on local street corners, to also get medical attention that way,” he said.

Cox said the disruption “could be very temporary.”

“But we thought it was important, particularly with the heat that we’re about to experience, to make sure that we give people the opportunity to know what’s going on,” he said.

Boston Mayor Michelle Wu said residents shouldn’t worry about calling the correct number or facility for their emergency, but to just reach out to their nearest authorities.

“If you are experiencing an emergency, if you find your way to police, fire or EMS, we will make sure that you get to the right place,” she said.

She said authorities were working to resolve the issue.

Several years ago, Massachusetts suffered sporadic 911 outages. At the time, it was blamed on outages from Louisiana-based CenturyLink, which affected some Verizon customers.