NASHUA — Firefighters from five engine companies and two ladder companies battled a two-alarm blaze on Blossom Street Sunday afternoon.

Firefighters responded at 3:53 p.m. to a report of heavy fire in the rear of the apartment building at 3 Blossom Street. Upon arrival, crew from Nashua Engine 2 determined the fire had spread across the first and second floors, and up into the attic.

Battling the hot weather as well as the flames, firefighters encountered heavy smoke conditions, but brought the fire under control by 4:17 p.m. All of the occupants of the building safely exited the structure, and firefighters were able to rescue two cats.

The fire was contained to the rear portion of the building.

A damage estimate was unavailable Sunday night.

The cause of the fire is not considered suspicious, but the state fire marshal's office will investigate to determine the cause.