A Utah military base that carries out tests to protect troops against biological attacks was locked down for nearly 12 hours overnight due to a "serious concern" before it was allowed to reopen early Thursday, officials said.

Dugway Proving Grounds spokeswoman Paula Thomas said the base, located about 85 miles southwest of Salt Lake City, had first reopened to incoming personnel, and people inside were allowed to leave shortly thereafter.

She said there were no injuries resulting from the cause of the lockdown. More details would be released later in the day, she added.

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