The at 55 Elm St. blaze affected an area south of Elm Street and prompted Hartford Hospital to switch to backup power, District Chief Mario Oquendo Jr. said.
Eversource crews isolated the electrical vault, allowing first responders to safely extinguish visible flames using dry chemical extinguishers. Officials say the cause of the fire remains under investigation, and there is no timeline for restoring power to the affected areas.
"Eversource will be working in the area for an unspecified amount of time," Oquendo said in a statement.
The Eversource outage map showed 1,055 outages as of 9:30 a.m.
Residents are urged to stay clear of the area while crews work to repair the damage.
This is a developing story. Check back for more.
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