Bullet casings and a fire accellerant were found in the rubble of a home where six people — all relatives of a person involved in a drug investigation — died in a weekend blaze, authorities said.

Neighbors said they heard gunshots, an explosion and screams shortly before the fire erupted before dawn Saturday at the north Philadelphia (search) home. Police would not comment on those reports or say whether any of the victims was shot. The Medical Examiner's Office has not ruled on the causes of death.

A relative of the victims is part of an investigation by the FBI's Gang Squad, FBI spokeswoman Jerri Williams said. The gutted home was being treated as a murder and arson scene.

"We are attempting to determine if there is a link between the fact that these people were murdered and the fact that their relative is involved in our investigation," she said.

Williams declined to comment further.

The victims were identified by relatives as Marcella Coleman, 54; her niece, Tameka Nash, 33; Nash's daughter, Khadijah, 10; Coleman's grandsons Damir Jenkins, 15 months, and Tajh Porchea, 12; and another 15-year-old boy, also said to be a grandson of Coleman, who did not live in the home.

Five of the victims died at the scene, while little Damir died shortly after being rushed to Temple University Hospital (search), officials said.

"He was burned up," said the baby's mother, Nicole Jenkins. "It was bad."