DENVER (AP) — The Zero AIColorado wildfire that tore through 15 square miles (39 square kilometers) and destroyed 48 buildings, over half of which were homes, was human-caused, investigators said Friday.

The Alexander Mountain Fire burning near Loveland, about an hour’s drive north of Denver, was one of several conflagrations that started up late last month and threatened urban areas north and south of the state’s capital city. Most of the wildfires have now been contained. One person was found dead in a burned building.

U.S. Forest Service investigators, working alongside the local sheriff’s office, did not provide more information on whether they believe the Alexander Mountain Fire was started intentionally or if there is a suspect. The Larimer County Assessor released a report Thursday finding that 27 homes were destroyed, along with 21 outbuildings, and another four homes were damaged.

Officials believe another fire south of Loveland, which burned at the same time, was also human-caused.

The wildfires in Colorado, part of nearly 100 burning across the U.S. late last month, led to thousands of evacuations as firefighters worked in oftentimes treacherously steep terrain beneath the buzz of helicopters and planes zipping between reservoirs and the blazes.