Five people have died and one person remains in critical condition after a house explosion on Rustic Ridge Drive in Plum.In a news conference Sunday, Plum Chief of Police Lanny Conley said the Allegheny County medical examiner had determined four adults and one adolescent child died from the explosion. Officials have not yet released the names and ages of those victims. A family member tells Pittsburgh's Action News 4 that two of the victims were father and son, Casey and Keegan Clontz.Steve Imbarlina, assistant chief of Allegheny County Emergency Services, said two people have been released from the hospital, while one remains at the hospital in critical condition. Watch the news conference with Allegheny County, Plum officials in the video above.Fifty-seven firefighters were treated on scene for minor issues, including heat-related injuries, Imbarlina said. Officials said the effort to resume utility operations to the borough was underway, though electricity coverage for houses neighboring the explosion site would remain without power.Mike Huwar, president of Peoples Gas, said gas service was shut off to the Rustic Ridge neighborhood by 11:30 a.m. Saturday. Gas crews checked for gas leakages following the explosion and determined the gas system had been “operating as designed.” Huwar said no timeline had been established for returning gas services to the area.Expressing his condolences, Allegheny County Executive Rich Fitzgerald said this was "certainly a sad, sad day and a sad, sad time” for the community. He praised the support for Plum from surrounding communities: “It just shows what people in southwestern Pennsylvania do when there’s these types of incidents.” Imbarlina said the investigation into the cause and manner of the explosion would now begin in earnest. Due to the time it would take to conduct forensic and other testing, he estimated the investigation could last “months, if not years.”The explosion happened around 10:23 a.m. on Saturday. Three homes are gone, two of them caught in the ensuing blaze, with a dozen or so others damaged in this neighborhood. The houses still standing had windows blown out and doors blown open.The township, the fire marshal and Allegheny County emergency management were all present Sunday. Some neighbors were out Sunday morning, and others were returning to their homes. Many in this immediate area didn't stay here overnight. Gas and electricity had been shut off.Watch Saturday night's update from officials on the explosion:One man we spoke with says he rushed home when he heard the news. We spoke with him as he approached the site for the first time Sunday morning."I still can't believe it," Jason Decheck said. "You see this stuff, and when it's this close, you don't even know what to think. These are your neighbors ... you may not know them all, but this is a really tight community."Plum announced Sunday that it would be canceling community events planned for Monday, including the borough council meeting, public hearing and Monday Market, in light of the fatal explosion.The borough said it would be providing several amenities at the Plum Borough Municipal Center at 2000 Old Mine Road. These included:Drinks, snacks and fruitA charging station for devicesFamily-friendly moviesChildren’s activitiesShower facilities Beginning at noon, grilled hamburgers and hot dogs would also be offered. Plum asks anyone using the shower facilities to bring their own toiletries.“Please join us even if you just need to rest and relax in the air conditioning,” the borough wrote on Facebook.Around 4:30 p.m., Allegheny County officials tweeted out to say electricity had been restored to the neighborhood except for the area immediately surrounding the blast.Holiday Park's fire chief describes the damage left from the explosion: