"People reported hearing three loud booms," said Cpl. Pam Jetsel, a spokeswoman for the Johnson County Sheriff's Department.
No one was injured, and about 200 employees of Owen Oil Tools were safely moved to the northern part of the 1,100-acre complex on Texas 171 between Godley and Cresson.
Cresson, Godley and Midnorth volunteer fire departments responded to 911 calls about 11:20 a.m.
Firefighters are letting the fire burn itself out, Jetsel said.
The explosives made in the building are put into wells to fracture rock to allow gas or oil to flow, Lt. Bobby Green of the Godley Volunteer Fire Department said.
The Bureau of Alcohol, Tobacco, Firearms and Explosives is investigating.
The Sheriff's Department didn't have a damage estimate Wednesday. Company officials did not return calls.
According to its Web site, Owen Oil Tools has a 213,000-square-foot production area, including a 70,000-square-foot hardware manufacturing plant that opened in November 2003 and a 22,500-square-foot materials warehouse completed last year. Owen does business worldwide.
Staff Writers Elizabeth Campbell and Martha Deller Contributed to This Report.
