Firefighters extinguished a two-alarm blaze in a downtown duplex Thursday afternoon.

Two families, including two adults and four children, were displaced and are being assisted by the American Red Cross, according to a news release from city spokeswoman Diana Klink.

One firefighter suffered injuries not considered life-threatening and was treated at Sentara Obici Hospital.

The fire was reported at 4:42 p.m., and the first units arrived two minutes later to find heavy smoke and flames showing from the second-floor rear porch of the two-story residence, located in the 100 block of Clay Street.

Witnesses said they saw firefighters revive a black kitten a firefighter carried out of the home. The witnesses, who work nearby, said one of the families just moved in a couple of weeks ago.

A for sale sign stood in the yard of the home.

Because of the extent of the fire and the proximity of homes, neighboring residences were evacuated as a precautionary measure. However, firefighters kept the blaze contained to the home where it started, and the other homes were not damaged.

The response was upgraded to two alarms because of the extent of the fire and proximity of homes, according to the press release.

Responding units from Suffolk Fire and Rescue included Engines 1, 2, 3 and 4, Ladders 5 and 6, Medics 1A, 6A and 9A, Rescue 1 and 6, EMS 1, Battalions 1 and 2, Rehab 6 and the Fire Marshal’s Office.

Carrsville and Carrollton volunteer fire departments and the Portsmouth Fire Department backfilled stations. The Nansemond-Suffolk Volunteer Rescue Squad and all of the city’s volunteer fire departments — Chuckatuck, Driver, Holland and Whaleyville — also provided assistance.

Several streets or parts of streets in the area were closed for much of the afternoon and evening. The fire was called under control at 7:17 p.m.

The cause of the fire is under investigation.