"We have an idea of where they are," Long said. "We didn't want to collapse anything."
The chief said he strongly believed the four men three workers and a supervisor, all of whom Long said he knew personally were the only people still unaccounted for from the blast, and he held out hope that they were still alive.
"We operate on the policy that everyone is alive until we get to them," he said.
Crews brought in heavy equipment Saturday to remove debris as investigators continued assessing what sparked the blast that ignited a storage silo. At least four flatbed trucks carrying segments of a giant crane and other machinery rolled through the refinery's front gates.
Imperial Sugar was one of the largest, and oldest, employers in this tiny city of 5,000 just a few miles west of Savannah. The sudden blast that rattled the city late Thursday engulfed the refinery in flames.
Investigators were unable to determine what sparked the explosion as firefighters stamped out flames inside the vast refinery a network of warehouses, silos and buildings eight stories tall connected by corridors of sheet metal.
Imperial President and CEO John Sheptor said sugar dust in a silo where refined sugar was stored before being packaged likely ignited like gunpowder. Sugar dust can become combustible if it's too dry and builds up a static electric charge.
The result was as devastating as a bomb. Floors inside the plant collapsed, flames spread throughout the refinery, metal girders buckled into twisted heaps and shredded sheet metal littered the wreckage.
More than 30 employees were rushed to hospitals as ambulances lined up a dozen at a time outside the refinery's sole entrance road.
Several were airlifted to a burn center in Augusta, 130 miles up the Savannah River. Many were in critical condition, including some who were placed on ventilators, said Dr. William Wessinger, the medical director at Memorial University Medical Center in Savannah. A spokeswoman from the Savannah hospital said Saturday that the last of nine workers who were treated there had been released.
Beth Frits, a spokeswoman for the Joseph M. Still Burn Center at Doctors Hospital in Augusta, said Saturday that 16 fire victims transferred from Memorial were in critical condition and three were in serious condition.
By Friday afternoon, the first deaths were confirmed as firefighters pulled three bodies from tunnels that ran beneath the refinery; a fourth body was recovered later in the day. None was immediately identified.
Company officials refused to speculate on when the plant might reopen, saying structural engineers would need to examine the damage.
Sugar dust is so combustible that static electricity, sparks from metal tools or a cigarette can ignite explosions.
More than 300 dust explosions have killed more than 120 works in grain silos, sugar plants and food processing plants over the past three decades. Most are preventable by removing fine-grain dust as it builds up, experts say.
Associated Press writers Russ Bynum and Bruce Smith in Savannah and Harry Weber in Atlanta contributed to this report.
On the Net:
Imperial Sugar: http://www.imperialsugar.com