Firefighters investigated over the weekend after a homeowner heard what he or she thought was an explosion. The resident heard the explosion overnight and called the fire department Saturday morning after finding a contractor’s equipment pile had burned, according to the Monroe Volunteer Fire Department’s Facebook page. A painter’s equipment likely naturally combusted and caused a flash fire that burned materials and shrubbery, the department said. Firefighters soaked the smoldering area, according to the Facebook post. The fire marshal and the state Department of Energy and Environmental Protection are investigating.