The U.S. Capitol Police is working with Dover, New Hampshire, police to investigate the source of suspicious package sent to a Rep. Carol Shea-Porter’s district office on Monday.

Around 1 p.m., the U.S. Postal Service delivered an envelope to the New Hampshire Democrat’s office that staffers quickly realized contained an “unidentified brown substance,” the congresswoman said in a news release.

“It was immediately apparent to them that they had concerns and they instituted their protocols and called us right away,” Dover police Lt. Brant Dolleman told the Union Leader in New Hampshire. Dover police handled the envelope “very quickly.”

The package did not injure anyone and did not prompt a hazmat response, Dolleman said.

“My office followed House procedure and notified the appropriate law enforcement agencies, and we are waiting for the results of some testing,” Shea-Porter said in her statement. “I am so grateful for the quick response of the Dover Police department.”

While Dolleman said he was unaware of similar suspicious packages delivered in New Hampshire, there has been a wave of threats against members of Congress over the last year.

In February, a Syracuse, New York, man pleaded guilty to threatening to kill GOP Rep. John Katko unless he supported net neutrality.

Last Friday, a Virginia man threatened to kill Rep. Scott Taylor with a shotgun over marijuana policy.

Last June at a GOP baseball team practice in Alexandria, Virginia, a gunman opened fire on Republican lawmakers and staffers, seriously wounding House Majority Whip Steve Scalise of Louisiana. Rep. Roger Williams of Texas suffered a broken ankle diving into the dugout for cover. One of his staffers was shot through the leg.

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