A three-alarm fire broke out in Somerville early this morning, displacing at least five people, fire officials said.

The fire began at a 2½-story residence on Banks Street near the intersection with Elm around 5:05 a.m., but spread next door, Somerville Deputy Fire Chief Patrick Sullivan III said.

“The fire spread to an adjoining dwelling, which upgraded the fire to three alarms,” Sullivan said.

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One resident was taken to a local hospital for smoke inhalation, Sullivan said.

A damage estimate has not been calculated, but neither residence will need to be demolished, Sullivan said.

Boston, Cambridge, Medford, and Everett fire crews assisted in battling the blaze, officials said.

The cause of the fire has not yet been determined.

“We have an investigator looking into the cause of the fire presently,” Sullivan said.