BOULDER COUNTY, Colo. (CBS4)– Investigators continue to look into what caused the Marshall Fire in Boulder County. The Boulder County Sheriff’s Office is investigating the possibility that an underground mine fire could be to blame.

A home burns in the Centennial Heights neighborhood of Louisville. (Photo by Marc Piscotty/Getty Images)

Investigators have focused their attention on the property of the Twelve Tribes religious group. There was a Boulder County Sheriff’s Office vehicle parked in the area on Friday night.

(credit: CBS)

The mine fire has been added to the list of possible causes.

Nearly 1,100 homes and businesses were lost in the fire. One man died and a 91-year-old grandmother remains missing.