Massachusetts’s statewide 911 emergency system was paralyzed on Tuesday afternoon as officials urged residents to call local police stations and firehouses and revert to pulling red fire call boxes on street corners if necessary.

Commissioner Michael Cox of the Boston Police Department said on Tuesday around 2 p.m. that the system was experiencing temporary issues, though it was unclear when it would come back online or why it was down. The news came at the top of a news conference intended to announce the parade for the Boston Celtics, who won the NBA championship on Monday night.

The 911 outage came as soaring temperatures brought the heat index to 90 degrees in Boston on Tuesday, with some interior parts of New England expected to approach as much as 100 degrees.

“We thought it was important, particularly with the heat that we’re about to experience that we’d give people the opportunity to know what’s going on,” Mr. Cox said, noting the looming heat dome expected to arrive on the Northeast in the coming days.

He directed residents to a list of local stations to call for assistance, including for medical attention.

The state’s executive office of public safety and security said on social media that they were “aware of a disruption to the 911 system” and were “investigating the cause.”

Paul Burke, the Boston Fire commissioner, suggested three different options, starting with calling the mainline for the fire department, pulling a fire box and lastly going directly to a firehouse.

James Hooley, the chief of emergency medical services in the city, said police, fire and E.M.S. share the same dispatch system so calling any local administrative number would connect residents to the needed agency.

“We bail each other out,” Mr. Hooley said.

In April, the 911 emergency system went down in parts of Nebraska and Texas, the entire state of South Dakota and Las Vegas. The outage was caused by a third party company that was installing a light pole.

This is a developing story.