LYNN (CBS) – Eastern Bank’s headquarters in Lynn was evacuated Monday morning after a fire and explosions rattled the building and staff.

Fire Chief James McDonald said a National Grid crew was replacing an old transformer with a new one in an electrical room when something went wrong.

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“They were disconnecting old equipment that still had energy to it,” said McDonald.

Bank employees said the fire alarm went off and as the building was evacuated, they saw smoke and heard explosions.

“It sounded like someone was setting off fireworks,” said employee Heather Mateo. “Everyone went running, it was kind of a scary scene.”

No one was seriously hurt.  Police said one woman fell on a curb as she was leaving the bank.

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Everyone inside was moved across the street to North Shore Community College.

About 500 people work in the building, which has been closed for the day. McDonald said there were at least 200 inside during the incident.

On it’s Facebook page, Eastern Bank said customers may notice some technical difficulties.

“Due to an electrical mishap at our Operations Center there may be sporadic outages to our phone and email services.”

The building houses the bank’s headquarters and customer call center. Those phone lines are expected to be back up and running by Tuesday morning.

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WBZ-TV’s Christina Hager contributed to this report.