An investigation is underway after an Irving apartment complex caught fire overnight Tuesday, damaging about 10 residences and displacing an untold number of people. According to the Irving Fire Department, officials received a call at 11:48 p.m. about a fire at the Calloway at Las Colinas apartments off Park Ridge Boulevard. Officials said when firefighters arrived at the scene, they could see the fire coming through the roof of the apartment building and called for a second alarm. A mother and son working for a trash collection company told NBC 5 they smelled the smoke and immediately started banging on doors to get people out safely. A total of 10 units were involved in the fire, officials said. No residents or firefighters were injured during the blaze. Fire officials said they are unsure how many residents were impacted by the fire. The investigation into the cause of the fire is ongoing.