NEW YORK (CBSNewYork) – Fire officials believe a house fire that left three people dead and two others critically injured was intentionally set.

“Fire Marshals have determined that yesterday’s fatal fire at 23-49 93 St was incendiary – an ignitable liquid was used as an accelerant. There were 3 fatalities and two critically injured in the 2-alarm fire. The investigation is ongoing,” an FDNY spokesperson said in a statement Thursday.

Flames broke out around 4 p.m. inside a two-story house on 93rd Street in East Elmhurst. Officials said a tenant on the first floor heard smoke alarms and called 911.

“It’s quite unusual at that time in the afternoon to have a fire trap five occupants in a private dwelling,” FDNY Commissioner Daniel Nigro said.

A 76-year-old man and his 6-year-old granddaughter were killed in the blaze.

The little girl’s 35-year-old mother, identified as Elizabeth Rodriguez, is in critical condition, along with her 10-month-old brother.

“I only saw a man on the floor, could see the soles of his feet. They were doing the chest compressions very vigorously, and you could see that he wasn’t responding,” said neighbor Japhet Zayas. “Later on, we saw the white sheets come out.”

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Most of victims were part of the same family. Some were visiting from the Dominican Republic.

“It’s hard to speak to them in the condition they’re in right now,” friend Jeyson Rodriguez said.

Sources told CBS2 the situation may have stemmed from a dispute between the homeowner and someone who had been staying there.

“Beautiful, lovely family. They opened their doors to help someone, and that’s how they get repaid,” a friend named Gabriel told CBS2’s Jenna DeAngelis.

He said the family was letting a 23-year-old friend of a friend from the Dominican Republic stay with them as a favor, but when issues arose, they asked him to leave.

“When they asked him to leave, (he) set the house on fire and set everybody in the house on fire,” said Gabriel.

The 23-year-old was also killed in the blaze.

As the FDNY and NYPD worked the scene, neighbors stood by in disbelief.

“On July 4th, they were out here doing a barbecue. Right in the same area they were doing the CPR, they were having a barbecue just a week earlier,” neighbor Japhet Zayas said.

Shayla Medina said all she could think about were the mother’s helpless screams.

“Why my baby, why my baby? She was hysterical,” she said.

Officials said the fire is still under investigation.