At least 55 units in the complex in a Trenton suburb were damaged in Tuesday afternoon's explosion, police said, including about 10 that were destroyed. One neighbor said it was like a bomb had gone off.
Late in the day, after authorities thought the blast had not caused any fatalities, the body of a woman was discovered on a car near the site of the explosion.
Officials were not able to identify the victim and are awaiting an autopsy for a positive ID and cause of death, said Lt. Ron Lunetta. He added that no one else was believed to be missing.
It was not clear Tuesday night if the woman who was killed was inside or outside a residence when the explosion occurred.
Ewing police planned to be at the site overnight to secure the area, but noted that efforts to continue their investigation would be hampered by darkness and the large amount of debris.
Authorities said a majority of the displaced residents would not be able to go home until Wednesday morning at the earliest. Some were being sheltered at a local fire house, while others were staying overnight with family and friends.
Officials planned a news conference for Wednesday morning at Ewing Town Hall to provide updates.
The events leading to the explosion began with a contractor working to replace electric service to the house that later blew up, officials from the utility PSE&G said. Around noon, the utility got a call that the contractor had damaged a gas line.
Crews were repairing the line about an hour later when, PSE&G spokeswoman Lindsey Puliti said, "there was an ignition."
The force from the explosion buckled windows in an apartment complex nearby, said resident Marsha Brown, and pictures fell from her walls.
"It felt like a bomb," she said.
She ran to the town house complex, saw a home engulfed in flames and two utility workers on the lawn with injuries that apparently included broken bones. She said she saw another worker on a sidewalk crying, being held by a woman.
At least one home was a blackened pile of rubble, and others had damage, including windows that were blown out. Debris was widely scattered, with insulation hanging in some tree branches.
"My body was shaking. I like to say I am calm, but I was shaking," said Brown, who had a day off from her job as an infant hearing screener at a hospital. "You could feel the flames, everything."
A resident of the complex, Bryan Gentry, drove home minutes after he heard an explosion and as he got closer, saw a black smoke cloud. The fire was intensely hot, he said, and he saw one person walking away from the fire who appeared to be stunned.
"It was just unreal," he said, adding that emergency crews responded "really fast."
The seven people injured were all utility workers, authorities said. Just three of those victims, all close to the blast, had to be hospitalized and none of those injuries was considered life-threatening, said Dr. Louis D'Amelio, trauma chief at Capital Regional Medical Center in Trenton. They included concussions, broken bones and minor shrapnel wounds, he said.
Normally during that time of day, most people in the neighborhood are at work and their children are at school, Gentry said.
Though the damage to the pipeline caused a gas leak that could lead to an explosion, the pipeline itself did not explode, a spokesman for the utility said.
Mulvihill reported from Trenton. Associated Press writer Kevin Begos in Pittsburgh also contributed to this report.