State House safe to reopen Thursday as investigators rule fire was an accident

The State House will reopen to employees and the public Thursday, two days after an electrical fire, which investigators deemed an accident, forced the evacuation of the state capitol.

The fire, which shuttered the building Tuesday afternoon and Wednesday, raised concerns about carbon monoxide levels inside, the State House superintendent announced.

"The power has been restored to the building and it has been determined that it is safe to reopen the building tomorrow," Superintendent Tammy Kraus said around 4:15 p.m. Wednesday. She added, "Air scrubbers will continue to operate throughout the evening and potentially tomorrow to absorb residual odors."

High-voltage wires that feed into a transformer in the State House's sub-basement caught fire just after 2 p.m. Tuesday, fire department officials said. This triggered a two-alarm response from firefighters and forced the evacuation of hundreds of lawmakers, building staffers and tourists. The fire also left an acrid smell lingering throughout the State House.

Investigators determined that the fire was not intentionally set, the Massachusetts State Police announced separately Wednesday afternoon.

"The fire resulted from electrical faults in two lines that run from an electrical vault near a guard shack to a pull box in the sub-basement of the Annex Building," State Police spokesman David Procopio said.

In her update, Kraus said the fire's impact was confined to the electrical room where it occurred and that the Bureau of the State House was working with Eversource "to identify the scope of repair and create a work plan that will include upgrading the transformer electrical lines."

Boston Fire Department Commissioner Paul Burke told reporters Tuesday afternoon that it was unclear what caused the wires to catch fire, but he said the equipment did not appear to be old or outdated. "It could have been the demand because of the air conditioning, it could have been anything," he said.

The State Police Fire and Explosion Investigation Unit, State Police-Government Center Barracks, State Police State Office of Investigations, Boston Fire Department, the Bureau of the State House, and a Department of Fire Services state electrical consultant conducted the joint investigation, Procopio said.

The State House was closed Wednesday "out of an abundance of caution while details of [Tuesday's] fire continue to be investigated," Kraus said in a statement Tuesday night.

The Massachusetts House had planned to hold an informal session Wednesday, but scrubbed that plan and instead plans to convene at 11 a.m. Thursday, Speaker Ron Mariano's office said.

The building's closure Wednesday also led to the cancelation of what would have been the first in-person meeting of Beacon Hill's "Big Three" — Gov. Maura Healey, Senate President Karen Spilka and Mariano — since June 12. A Healey spokesperson said the trio planned to meet Wednesday afternoon, but postponed the meeting in light of the closure. The meeting has not yet been rescheduled, the governor's office said.

State House workers and guests were evacuated from the building twice on Tuesday. The first alarm, which sounded around 11 a.m., was "accidentally triggered" by two tourists, Procopio said. A separate investigation "determined that the visitors pulled the alarm under the mistaken assumption that it was a mechanism to open a door" and that the morning incident was not related to the afternoon's fire, he said.