An overnight fire in north Edmonton that destroyed one house under construction and badly damaged two other homes was arson, say investigators.

The fire, at 128th Avenue and 121st Street, was deliberately set, causing an estimated $660,000 in damages, said Edmonton Fire Rescue.

The fire was started around 1:30 a.m. in a two-storey fourplex that was under construction. About 50 firefighters responded, bringing the fire under control in about two hours.

The building was completely destroyed, but the fire also caused extensive damage to homes on either side of the property — an unoccupied detached house and a duplex. There was also minor damage to other surrounding properties.

Nobody was hurt during the fire.

Johnny Woldmichael, who was sleeping in the basement of the duplex, woke up to screams and shouts.

"The house next door was completely engulfed in flames," he said.  

All seven people living in the duplex escaped safely, but the home is all but destroyed with the entire roof caved in, he said.

The family had lived in home for five months.