Officials in a Maryland suburb of the nation's capital say they will investigate why the county's 911 system failed for two hours recently, during which time two people died.

Officials said in a statement Monday that the Montgomery County 911 system was out from about 11:10 p.m. Sunday until 1:10 a.m. Monday. Callers received only a busy signal.

During the outage, crews responded to two medical emergency calls involving fatalities, including that of a 91-year-old woman and a 40-year-old man. It's unclear if the outage was involved.

County Executive Ike Leggett says he's requesting an immediate investigation.

County chief spokesman Patrick Lacefield says the 911 outage was traced to a malfunctioning heating and air conditioning system that caused both the main power system and backup system to shut down.