Firefighters responded to 22 Porter St. at about 12:30 p.m. Wednesday to put out a fire between the first floor and the basement wall of the home, according to Somerville Fire Chief Kevin Kelleher.

There were no injuries, but the house incurred a "substantial amount of damage" as firefighters tried to get at the fire under the floor, Kelleher said.

He said there was smoke and water damage, and the building would not habitable until repairs are made.

Three people were likely to be displaced Wednesday night. A family that lived in one of the units of the building was on vacation when the fire struck, but they were planning to return soon, meaning six people were likely to be displaced "for a short period of time," the fire chief said.

Kelleher said it was a "tough day for the firefighters" due to the heat and humidity and the physical work involved in gaining access to the fire underneath the floor, which involved a lot of chopping.

A fire investigator was still on scene as of Wednesday afternoon.