Some soldiers at Fort Hood said they were warned not to support certain political groups.
The Washington Times said Tea Party and evangelical religious groups were singled out during training.
The conservative Liberty Institute in Plano is investigating.
"It's pretty scary for the United States Army to suggest or outright say as its alleged here that evangelical Christians are a domestic terror threat. Makes it a scary time to come out of the closet as an evangelical," said Hiram Sasser with the Liberty Institute.
Commanders at Fort Hood said they launched their own investigation into the report.
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