This breaking news story will be updated as more information becomes available.
1:17 p.m.: Williams Cos., the parent group of Williams Olefins, has said that the blast took place at 8:37 a.m.
"Emergency shut-down valves have been closed. The unit is isolated," the company said in a written statement, according to Reuters. "We are in the process of accounting for all personnel. Injuries have been reported, the number and extent of those injuries is not known at this point."
1:15 p.m.: Officials said the scene had been stabilized and the fire has been contained as of 10:50 a.m., WAFB-TV reported, but Louisiana State Police said a secondary explosion could still occur.
1:06 p.m.: Officials say that 30 people were taken from the scene of the explosion by ambulance, while as many as four were transported via helicopter, according to the according to the New Orleans Times-Picayune newspaper.
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1:02 p.m.: A witness who was the scene shortly after the blast shot the following video -- which was first obtained by WAFB-TV -- of its aftermath:
Many are feared dead from a massive explosion that rocked a chemical plant in Geismar, La., Thursday morning. The explosion set off a large fire, and stunning photographs from the scene just south of Baton Rouge show billowing flames and dark black smoke pouring out of the facility.
Authorities say that the number of fatalities may be "very high," according to RT.com.
The Iberville Office of Emergency Preparedness reported seven injuries shortly after the explosion, according to local news station WAFB.
The explosion at the Williams Olefins-owned plant took place at about 8:30 a.m. Thursday, and witnesses reported seeing a fireball rising in the air, the Times-Picayune reported.