SOUTH BOSTON (CBS) -- It was a tough night for Boston firefighters as they struggled to put out a large blaze in a building without a first floor.

The fire broke out just before 10:30 p.m. Monday night in an East 4th Street brownstone.

Arriving firefighters were greeted by heavy flames, and faced additional challenges when they realized the building was under renovation and missing a first floor.

The fire quickly reached four alarms and was knocked down at about 11:00 p.m., but not before spreading to two other buildings. Two of the three buildings were vacant.

The Boston Fire Department said the fire was caused by floor-finishing materials, including oily rags, that were stored in the building next door to the one being renovated.

A crew was still on scene Tuesday morning to board up blown-out windows.

Five people were displaced as a result of the fire.

Between the three buildings, firefighters estimated the damage at $1 million. There were no injuries.