PHILADELPHIA — An early Sunday explosion in North Philadelphia resulted in one fatality and injuries to two others, as reported by officials. The blast completely demolished three row houses and caused damage to several adjacent properties.

Firefighters from the Philadelphia Fire Department, accompanied by a search dog, were actively exploring the debris in the Nicetown area on Sunday afternoon. Their focus was on searching for victims and uncovering the cause of the explosion, stated Daniel McCarty, who serves as the executive officer of the fire department.

The reason behind the explosion and subsequent fire remains unknown, according to McCarty. He added that the federal Bureau of Alcohol, Tobacco, Firearms, and Explosives is participating in the ongoing investigation.

The explosion occurred around 4:50 a.m. local time Sunday in the 1900 block of West Bristol Street in the Nicetown neighborhood of North Philadelphia, authorities said.

When firefighters and police officers arrived at the scene, they found three attached row houses completely collapsed and on fire, according to officials, who said firefighters and police immediately began searching through the wreckage and pulled two women from one of the collapsed residences.

The badly injured women were taken by ambulance to a hospital. One of the victims was in critical condition and the other was in stable condition, McCarty said.

During a secondary search, a search-and-rescue dog alerted crews to a possible body buried in the debris, a Philadelphia police official said.

“After pulling through some of the rubble, we were able to find that we actually did have a victim that was in the collapse. It was also determined that the victim at that point had deceased in the collapse,” the police official said during a news conference.

Philadelphia Mayor Cherelle Parker said she went to the hospital to check on the two injured women and spoke to their families.

“Philadelphia, we want to ask that you lift them up in prayer,” Parker said. “To all of the families, we are lifting you up in prayer, and the City of Philadelphia will remain here and on the scene to ensure that anyone who has been directly or indirectly impacted receives the support and services they need.”

The explosion, according to McCarty, left numerous homes in the blocks surrounding the collapsed residences with broken windows and other structural damage.

McCarty said multiple vehicles in the area were also damaged and buried under debris.

Rocky Dotson, who lives two blocks away from the explosion, said he heard the blast.

“I’m sitting down in the living room watching TV and all of a sudden, I hear like a ‘boom,'” Dotson told ABC Philadelphia station WPVI.

Dotson said that before he went outside to check on the noise, a relative called him and told him that homes had been destroyed by an explosion near his house.

“I came out and it was just total chaos,” Dotson said of seeing firefighters and ambulances rushing to the scene.

Dotson said he had just walked by the houses that were destroyed on Friday. “To not see those homes there is crazy,” he said.

McCarty said PICO, the Philadelphia electric utility, and Philadelphia Gas Works were on scene Sunday assisting in the investigation. He added that about 10 homes in the area of the explosion have been evacuated and that a temporary emergency shelter had been opened.

Investigators are “going literally brick by brick to discover evidence to identify what happened here this morning,” McCarty said.