BY REBECCA BENNETT — Updated at 8:36 p.m.  According to Pepco, approximately 630 customers were reportedly without power just after 7 p.m. on Sunday evening. The area affected is the Hyattsville Historic District and homes west of DeMatha Catholic High School. Pepco is currently reporting that 350 of those customers remain without power.

A spokesperson from Pepco said that Mylar balloons made contact with some of Pepco’s electrical equipment and caused the outage. Mylar balloons are made of foil, where as other balloons may be made of latex.

Residents reported hearing sirens around the same time, which were for a building fire caused by a faulty vent near Jefferson Street and Baltimore Avenue, according to the Riverdale Volunteer Fire Department. Pepco said the building fire was unrelated.

Some residents reported the power coming back on just after 8 p.m. Sunday evening. Pepco says it expects power to be returned to all homes in the area sometime tonight, even though crews estimated 9 p.m.

FOX13 in Salt Lake City provided information about what happens when Mylar balloons hit power lines.