Two blocks of townhouses under construction in Barrhaven caught fire early Monday morning, and the Ottawa police arson unit is investigating.

The flames broke out on Mancini Way near Chapman Mills Drive just before 3 a.m. Monday.

The fire affected 16 units in the two blocks of townhouses, according to Ottawa fire officials. Damage is estimated at more than $1 million.

Fire crews were forced to battle the flames from outside the two townhouse buildings. (Submitted by Michel Monette)

Heavy machinery will be brought in Monday to knock down the badly damaged sections of the buildings, according to Ottawa fire department spokesperson Danielle Cardinal.

The intensity of the fire — which reached a third alarm — forced crews to take a defensive position outside the buildings as they fought the blaze.

Some of the siding on nearby buildings was damaged by the heat.

No injuries have been reported.