The victims' identities were not immediately divulged. Late last night, federal and county investigators were looking into the possibility that the blast was linked to a domestic dispute.
Bomb-detecting dogs were brought to the Ross Ridge Apartments complex near Rossville Boulevard to check out a car for other explosives, but police said nothing was found there.
Apartment residents said that a man estranged from his wife -- and believed to be a blast victim -- had threatened her Sunday at a family gathering.
One resident, who did not want to be identified, quoted the man as saying, "I'm going to blow you up."
At the shopping center, investigators said the search for evidence will continue into daylight hours today. All that remained of the vehicle that held the bomb was a charred, unrecognizable shell.
"It looked like a war zone," said Norman Rush, a barber who works at the shopping center. "It looked like they had walked on a land mine."
The blast, from a bomb inside the vehicle, occurred shortly after 6 p.m. and left a scene of bloody devastation, according to police officials and eyewitnesses.
"It was like an earthquake," said Albert Kellner, 35, who lives in the 900 block of Essex Ave., less than 100 yards from the blast. "It vibrated the house and me. It knocked me back."
He ran to the blast site. "It was incredible," he said. "I never smelled anything like that, and I never saw anything like that in my life, and I never want to see it again."
At least two dozen area businesses were ordered to close early.
Capt. Brian Uppercue, a county police spokesman, said the blast occurred in an alley behind the shopping center, where trash bins are kept.
Police believed that all the victims were inside the vehicle, thought to have been a blue or white minivan -- although a partial license tag that was found was registered to a station wagon.
"The whole ground shook, and the lights went out," said Tina Logue, 26, a stylist at the Hair Cuttery at Middlesex Shopping Center, near Essex and Marlyn avenues.
Bryan Linaweaver, 16, one of the first people to arrive at the site, said he was sitting on a porch less than a half-block away when it happened.
"The van was on fire on the right, and to the left of the van there was a body," he said. "I saw kinds of pieces of fender, glass and trash everywhere. . . . It was the loudest explosion I've ever heard before. . . . The whole thing just makes me sick."
John Wallace, who lives nearby, ran to the site when he heard the explosion and said he found the van engulfed in flames.
"It sounded like a loud boom," said Matt Fields, 17, who also lives nearby. Mini-explosions continued to go off inside the vehicle, he said.
Mr. Rush and Skip Frock, another barber, also ran to the scene, behind a NationsBank branch and a J. J. Newberry variety store. Mr. Rush watched as his co-worker and a police officer pulled a seriously injured child from the devastated van.
One of the victims, described as a girl about 9 years old who was moaning and crying, died at Johns Hopkins Hospital less than two hours later.
In other areas of the shopping center, employees huddled in their stores immediately after the explosion. "I was scared," said Pam Kimm, manager of Middlesex Liquors, as she closed her store early.
Lillian Smuteck, manager of Videos 4 You in the 1200 block of Eastern Blvd. across from the shopping center, said the force of the blast knocked out the store's computers, shook the windows and pulled the doors open. Others reported their electricity went off, and items were knocked off walls and tables.
Whistles and whines, typical of incendiary devices, were heard by arriving police officers, suggesting that it was more than a gas tank explosion.
Bomb experts from the Baltimore County police and federal Bureau of Alcohol, Tobacco and Firearms joined homicide detectives and scores of local and state police and fire officers at the site. The area was cordoned off as they began the task of identifying evidence and determining the source of the explosion. Police said they found explosive material around the car.
Several pieces of evidence landed outside the area that police had roped off, eyewitnesses said. Crumpled metal from the van was found as far as 75 yards away from the remaining twisted hull of metal. Its engine was unrecognizable.
Sam Cavanaugh, a mechanic visiting friends at Eastern Auto on Old Eastern Avenue -- about 400 yards away -- said he "felt a blast, a gush, pressure. I saw debris going over me." Mr. Cavanaugh, 18, said he immediately drove to the scene. "I saw car parts. I saw a piece of a steering wheel. I saw a windshield . . " as well as body parts, he said, visibly shaken.
Authorities set up a command center on the lawn of Trinity Temple Interfaith Church, where neighbors stood crowded around in an attempt to see past the emergency vehicles to the blast site.
When Baltimore County Executive C. A. Dutch Ruppersberger III arrived, he pointed 20 feet up into a tree. "As you can see, there are car parts in the tree," he said, asking people to stay back. "We need to do everything we can to preserve evidence."
Malinda Foster, a Perry Hall Elementary School teacher who lives a block away, said she went outside with her two sons, Steven, 14, and Ryan, 11, after hearing the explosion, which shook her house.
Erich Riessler, 57, felt the shock as he lay on the floor of his Oberle Avenue home, also a quarter-mile away. His wife, Jean, 55, said, "Things like this don't happen in Essex."