State Department of Public Safety spokesman DL Wilson said it will be some time before authorities know the full extent of the loss of life and damage caused by the blast at the blast at the plant in West, about 20 miles north of Waco.
The explosion at West Fertilizer happened shortly before 8pm local time, could be heard 45 miles away and damaged buildings over a wide area.
The mayor of West said some firefighters who were battling a blaze when the blast happened have not yet been accounted for.
Tommy Muska said there were five or six volunteer firefighters battling the blaze at the West Fertilizer plant when the explosion went off, and not all of them have been accounted for.
Muska, a volunteer firefighter himself, said the blast knocked his helmet off and shattered the windows of his nearby home.
Country music legend Willie Nelson sent out his prayers after the blast hit near where he grew up.
"West has been in my backyard all my life," he tweeted. "My heart is praying for the community that we call home."
When not on the road touring, Nelson has lived in Austin, Texas, since 1971, but he was born and grew up 120 miles north of the state capital, in Abbott, which is about five miles north of West.
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