U.S. Capitol Police reopened the Capitol visitors center Tuesday morning after authorities determined that suspicious substance found there was not hazardous.

It was unclear what the substance was, but Officer Shennel Antrobus said authorities reopened the center at 10 a.m. Tuesday.

Police were called to the U.S. Capitol’s Emancipation Hall around 9:10 a.m. after the substance was discovered in the center.

The nearly hour-long investigation did not close the U.S. Capitol.

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