SHELTON — Two pets were killed, a dozen residents were displaced and two firefighters were evaluated in a late Saturday night fire that damaged a mixed-use building on Howe Avenue.

The fire also affected four businesses, City Stylez Barber Shop, Little Petting Zoo, M&T Nail & Spa Salon and Formal Massage, in the building, Chief Fran Jones said.

About 30 animals, including snakes, lizards, rabbits and birds, were rescued from the building, but a chinchilla and parakeet could not be saved, Jones said.

He said VCA Shoreline animal clinic sent the surviving animals to its North Haven facility.

Jones said the fire started a few minutes before midnight and took several Shelton crews and Derby firefighters until around 12:30 a.m. Sunday to extinguish. But firefighters stayed throughout the night to complete overhaul and assist residents, he said.

Red Cross is helping the 12 tenants whose apartments were damaged, Jones said.

The two firefighters who were treated by emergency medical services are O.K. and were released, he said.

The building was built between the 1870s and early 1900s, making it more difficult to knock down the fire, Jones said.

“Shelton and Derby firemen did a tremendous job,” he said.

The fire marshal is investigating the cause of the fire, but a majority of the damage was in a common basement used by the stores, Jones said. The first, second and third floors suffered smoke damage. The building is inhabitable and does not have power or gas, he said.