The blast Wednesday at the West Pharmaceutical Services Inc. plant shot flames and debris high into the air and shook buildings miles away.
Investigators from the U.S. Chemical Safety Board said they identified several potential sources of explosive dust from rubber processing operations at the plant.
They said they are looking at a suspending ceiling in the first floor of the two-story, 40-foot-tall processing area, on the theory that rubber dust may have accumulated there.
They are also examining whether a large explosion on the first floor may have been triggered by a smaller blast of unknown origin.
"Plant employees told the investigators that the rubber mixer on the upper level had experienced previous internal fires, including one strong enough to blow off the mixer door," the CSB said in a news release. "Investigators do not yet know the number or nature of these fires or whether there is a connection between these mixer fires and the events of Jan. 29."
The independent federal agency was holding a briefing at the plant Monday afternoon to discuss its findings.
In its news release, the agency said materials used at the site that could have caused a build-up of explosive dust included sulfur, polymer powders and other organic processing agents.
"Dust can be an insidious hazard wherever finely divided organic materials are used," investigator Steve Selk said. "While some of these materials might appear to present a limited fire hazard, when suspended in air under the right conditions these same materials can explode with deadly consequences."
It took several days after the blast before investigators could enter the demolished factory where synthetic rubber was produced in one area and shaped into syringe plungers and intravenous equipment parts in another.
Mourners packed a Garner funeral home Monday to bid farewell to one of the victims of the plant explosion.
Kevin Cruiess, 22, survived the blast, but later died Friday at the North Carolina Jaycee Burn Center.
Funeral services were also held this weekend for the three other victims: 51-year-old William Gray of Snow Hill, 60-year-old James Byrd of Dover and 50-year-old Faye Wilkins.
About 130 people were inside the medical supply factory at the time of the explosion. Nine remained in critical condition Monday at the North Carolina Jaycee Burn Center in Chapel Hill.
Copyright 2024 by WRAL.com and the Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
