A woman and her two children are lucky to be alive after a fire broke out in their southwest Calgary home, and then spread throughout the fourplex, threatening several other units.

At around 3 a.m., officials say crews were called to a residential complex located at 71 Lincoln Green S.W.

When they arrived at the scene, they immediately called for a second alarm, given the large amount of smoke and flames coming from the second floor of one of the units.

Four homes, including the structure which was the source of the blaze, were evacuated with 12 people getting out safely.

Five of those residents were children.

The family who lived in the house where the blaze started were alerted by smoke alarms.

Crews were able to get the blaze quickly under control by fighting it from within the main unit, knocking the fire down in just under an hour.

One resident says that police arrived at the scene first, followed by frefighters. "Nobody was hurt, everybody was out of the house," Shaquila Kashwantale said. "They came and they were able to put out the fire. It took a long time because it was a big fire."

She says that a number of residents were trying to put out the fire before crews arrived at the scene, but weren't successful. "The fire got bigger and came outside."

"It's very sad because everything is destroyed. It was very scary."

Officials say that one unit has been completely destroyed and three other attached units have sustained smoke damage and some exterior damage.

Fire officials said they did have a concern that another person was still inside the burning home when they arrived.

"The real fear was the possibility of a child," said Carol Henke, public information officer with the Calgary Fire Department. "We did find out everyone made it safely. A family cat did not, and was found deceased upstairs."

The woman and her two children who lived in the home where the fire started, were taken to hospital for treatment, but officials say their injuries were not a result of the fire.

The fire sparked in the main floor of one of the units, but investigators are still at the scene, working on determining a cause.

Two of the families are back inside their homes, and the Red Cross is helping the families who are still displaced.