DENVER -- A fire that tore through a Northeast Denver strip mall and destroyed eight businesses over the weekend was the result of arson, the Denver Fire Department said Tuesday.

Fire investigators said initially that the fire did not appear to be criminal in nature but that is not the case, a source told 7NEWS.

"Evidence has been discovered which confirms the elements of an arson fire," Denver Fire Lt. Phil Champagne confirmed.

Denver police, the Colorado Bureau of Investigation and the Bureau of Alcohol, Tobacco and Firearms (ATF) continue to investigate who set the fire and why but no further information was released.

The fire at Holly Square Shopping Center at 34th Avenue and Holly Street was first reported around 4 a.m. Sunday.

The flames shot up 30 to 40 feet in the air, quickly spreading through a common wooden ceiling. The gutted the 36,000 square-foot complex before firefighters could contain it three hours later.

Nearly 70 firefighters were called to the scene. They tried to battle the blaze from the inside but had to be pulled out when the building was in danger of collapsing.

The estimate of the damage has not been released. There were at least six shops that were open for business, including a Family Dollar store, a liquor store, Tyson's Market, and a dental office. A day-care center at the end of the structure the mall was saved because of a firewall.

Neighbors said that the mall was a gathering spot for people in Park Hill.