LIVERMORE (BCN) — Twenty-one people were displaced after a triplex apartment building caught fire early Sunday morning in Livermore.

At 3:01 a.m., firefighters responded to a report of a fire at an apartment building on Chestnut Street, according to fire officials.

Upon arrival, firefighters saw flames coming from the front windows and door of a second floor unit, fire officials said.

Firefighters were able to quickly contain the fire to the unit.

A family of four was able to escape the fire from their second floor apartment, according to fire officials.

All 21 occupants displaced by the fire received help with relocation from the American Red Cross.

The fire remains under investigation, fire officials said.