A fire at 12 Drayton Ave. that was called in around 3:50 a.m. displaced four residents and sent one firefighter to the hospital with a non-life-threatening injury, the Boston Fire Department reports.

Investigators are now looking to determine the cause of the blaze, which the department says did an estimated $150,000 in damage.

Firefighters were hampered in their work by two hydrants that were frozen up, the department adds.