A firefighter stands on a rail line and surveys the remains of a fertilizer plant destroyed by an explosion in West, Texas, Thursday, April 18, 2013. (AP Photo/LM Otero)
Federal investigators say they will begin inspecting the site of the devastating fertilizer plant explosion in an effort to collect debris and other evidence that may point to a cause of the fatal blast.
Franceska Perot, a spokeswoman for the Bureau of Alcohol, Tobacco, Firearms and Explosives, says investigators will begin Friday at the perimeter of the blast and work inward toward the destroyed West Fertilizer Co.
The ATF is scouring the site along with the state fire marshal's office.
The U.S. Chemical Safety Board says their investigators arrived on the scene Thursday and will begin visiting the scene of the explosion on Friday.
"A total of 12 investigators, including experts in fire and explosive modeling, will be assessing the area of impact to determine the cause and contributing factors of Wednesday's explosion," the board said in a statement.
As investigators move inward in examining debris and damage, residents gradually will be allowed to return Friday to homes along streets that have already been examined.
The bodies of 12 people have been pulled from the wreckage of the plant. Approximately 200 people were injured in the explosion Wednesday night.