The investigation will center on a 40,000-gallon tank that had been modified and did not have a pressure-relief system, agency investigator Johnnie Banks said Friday.
The tank at the Marcus Oil & Chemical plant in Houston was about 10 percent full when it exploded on Dec. 3. The blast was felt about 25 miles away and blew out windows and damaged homes and buildings near the facility.
Two firefighters and at least nine nearby residents suffered minor injuries.
Investigators have not determined whether excess pressure caused the explosion.
The tank contained a raw material used to make polyethylene wax, investigators said. The wax is used in paint and printing ink.
The agency opted for the formal investigation, which is expected to last a year, because of the size of the blast and because it caused injuries, Banks said. The agency could have opted to conduct a variety of shorter inquiries.
Officials with the Occupational Safety and Health Administration also are conducting an investigation.
Additionally, an attorney representing 27 people who live near the plant plans to file a lawsuit against Marcus Oil on Monday. The suit will seek compensation for damage to property and injuries caused by the blast and fire, attorney Monica C. Vaughan said.
Related :