Between 2003 and 2006, archaeologists from Arizona State Museum and volunteers from Earthwatch excavated the ancestral Hopi village of Chevelon, located 9 miles from Homolovi, and found a much higher percentage of burning there than at other sites in the area, raising questions about why so many rooms had burned. Possible causes included accidental environmental fire such as wildfire, lightning, or spontaneous combustion, conflict or violence, and community-related burning such as ritual closing, remodeling, or pest control. To test which explanation best fit the fires at Chevelon pueblo, archaeologists built replica pueblo rooms using materials identical to those recovered in excavations, including sandstone rocks, mud mortar, layered roof beams, branches, brush, and a final layer of earth, then burned them and analyzed the charred remains with fire investigators. Their experiments found that an accidental fire starting from the cooking hearth did not successfully ignite the roof, that an intentional fire started at the ceiling could easily cause the roof to collapse in 10 minutes, and that in either accidental or intentional fires, closing the roof hatch and opening side entrances greatly increased the burning. Corn can also spontaneously combust under the right conditions, and stored corn in Native American pueblos may have caused some burned structures at archaeological sites.