About a dozen firefighters were injured while battling a four-alarm fire on Milwaukee's south side Friday night.

The fire was first reported at 7:41 p.m. in the attic of a vacant house in the 2400 block of S. 8th St., but spread to a house to the north and quickly escalated. The vacant house was destroyed, and 12 people living in three units in the second house were displaced.

About 100 firefighters responded to the fire, along with at least 16 ladder trucks and engines and five paramedic units, according to Salvatore Santoro Jr., 4th battalion fire chief.

It was hot and sticky Friday night, with temperatures in the 80s.

Firefighters worked in rotations, fighting the blaze for 15 minutes and then taking half-hour breaks to rest and rehydrate, Santoro said.

Some of the minor injuries suffered were related to firefighters falling off water-laden equipment, he said. While the dozen firefighters were taken to local hospitals, none of the injuries appeared to be life threatening, he said.

"It was mostly bumps, bruises, scrapes and strains, but the heat certainly didn't help," Santoro said.

Besides the sweltering weather, Santoro estimated the temperature inside the burning structures was about 800 degrees.

The fire was under control by late Friday night. Water used to extinguish the flames came from as far as two blocks away, Santoro said. Smoke hung over the entire neighborhood.

Francisco Donan, 37, said his mother and 11 relatives lived in three units in the house where the fire had spread.

"They lost everything," Donan said.

Linda Lyndanicely, spokeswoman for American Red Cross, said the 12 displaced people were being helped by the Red Cross.