Investigators on Thursday began searching a house they believe was intentionally set on fire during a shooting that left two police officers injured and six people, including children, unaccounted for.

Police responded to a call Wednesday afternoon that an 11-year-old child had been shot in East Lansdowne, just outside Philadelphia. They were met with gunfire when they arrived at the house, and two officers sustained gunshot wounds.

Then, smoke and flames erupted at the house − a blaze authorities believe was deliberately set.

Delaware County District Attorney Jack Stollsteimer called the search for remains in the house "gruesome," describing it as a recovery operation.

What happened at the house in East Lansdowne?

The house in East Lansdowne was still smoldering Thursday and crews were concerned about the structural integrity of what was left of the home. That initially prevented them from searching for anyone who might have been in the home when the fire broke out, including the still-unidentified shooter and any other occupants at the home.

Stollsteimer said it was unclear whether the initial report of an 11-year-old child being shot was authentic or a ruse to draw officers to the house. The Philadelphia Inquirer, citing law enforcement sources, reported Thursday that the shooter was likely the person who called 911; it also reported that two families related to one another lived in the house and had no prior contact with law enforcement.

"It's a crime scene, but it's a recovery operation," Stollsteimer said, adding that the investigation into who might have been in the home could take "hours, even days."

The basement of the three-story house was flooded with about six feet of water from firefighters' efforts, which were delayed until police were sure the active shooter situation was over and no additional responders would be endangered.

Who lived at the home?

At a news conference Thursday afternoon, Stollsteimer said the Le family lived in the home and that three adults and three children were presumed dead inside. Authorities said earlier up to eight people may have been in the house.

Detectives doing what the DA called the "awful, horrible work of trying to find out where everybody is” discovered one human torso and one rifle, Stollsteimer said. Authorities likely will have to rely on dental records to identify the dead, he said.

"It will be a gruesome, time-consuming process," he said.

Two family members whom Stollsteimer identified as the grandparents of the children and parents of two adults living in the home were outside the home when the fire broke out.

A woman identified as the grandmother of the children told 6ABC that the incident stemmed from a dispute between her son and his 13-year-old niece and that her husband took her from the house when the argument escalated. The station reported that she told them her grandchildren, ages 10, 13 and 17 were all dead.

2 police officers were shot when responding to the scene

"Two of our members were shot today in the line of duty," the Delaware County Fraternal Order of Police Lodge No. 27 posted on social media Wednesday night. "... Our thoughts are with the officers, their friends and family as we hope for a speedy recovery. Thank you to the members who conducted a tactical rescue under fire to save the officers."

The Delaware County District Attorney's Office identified the officers Thursday.

Lansdowne Police officer David Schiazza, 54, suffered a gunshot wound to the leg and was to be released later Thursday afternoon. East Lansdowne Police officer John Meehan, 44, was shot in his left arm that required "a lengthy surgery," the agency said. His release date was still unknown as he continued to undergo treatment. Both officers are 22-year law enforcement veterans.

Lansdowne Borough Mayor Magda Byrne called the incident "one of the most tragic and scary events I have ever experienced in my 10 years as an elected official," vowing her borough's support for its neighboring town and offering thanks and support for the injured officers.

"Please hug your families a little tighter today," she added. "While you are at it, hug your neighbors too because they may need it."

Contributing: Associated Press