Seth Moulton

Federal authorities are investigating "suspicious mail" received by the Massachusetts Secretary of State's Office and Democratic Congressman Seth Moulton's Salem office on Friday.

"Late this morning, the Secretary of the Commonwealth’s office received an envelope by mail matching the description of suspicious mail received by other election offices around the country," Secretary of State William Galvin said in a statement Friday. "The envelope, addressed to the Elections Division, was not opened."

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He said his office contacted state and federal authorities immediately, and the envelope is now in the custody of the U.S. Postal Inspection Services and is now under investigation by federal authorities.

“I am grateful for the swift response this morning by the Massachusetts State Police, FBI, and USPIS,” Galvin said. “Because of the information we received from the FBI and USPIS before this envelope arrived, my staff was able to identify the envelope before it reached the Elections Division’s office. The Elections Division’s work was uninterrupted, and my staff remains focused on administering the upcoming election."

Galvin explained that an employee sorting through the mail found the envelope in question.

"He immediately acted, Galvin said. "He put on gloves and mask, and a plastic container was provided for the material."

Salem police said they responded to Moulton's office at 21 Front St. in Salem on Friday morning for a report of a "suspicious parcel" delivered through the U.S. mail.

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"The parcel, which contained an unknown powdery substance, was secured and safely removed from the building by law enforcement," police said. "The substance is currently being analyzed at the State Crime Lab. This incident is similar in nature to recent reports of suspicious packages being sent to election and congressional offices nationwide."

Moulton's office confirmed that they received a suspicious letter, addressed to the congressman, and reported it.

"Out of an abundance of caution, using the guidance given by the House Sergeant at Arms in response to the nationwide reports and investigation, Congressman Moulton’s staff did not open the letter and instead, immediately reported the letter to Salem Police Department (SPD) and the US Capitol Police. The FBI was subsequently notified," a spokesperson said in a statement.

The statement added that testing of the powder found nothing harmful.

Rep. Stephen Lynch's team also said a suspicious envelope was sent to his office in Brockton.

Rep. Lori Trahan's press office confirmed it received a letter in Lowell, as well.

Rep. Ayanna Pressley also said authorities were investigating a suspicious letter.

"Congresswoman Pressley's district office received a suspicious letter that matched the description of those sent to offices across the country," a spokesperson said. "Federal and local law enforcement were notified, Boston PD arrived on site, and they are currently investigating. The safety of her staff and all public servants is paramount to the Congresswoman."

"Our office has received a suspicious letter, which has been retrieved by USPS inspectors," Georgina Burros, communication director for Rep. Jake Auchincloss' office, said in a statement. "We continue to follow the guidance of SAA and are grateful to local and federal law enforcement for ensuring the safety of our staff."

Burros said the letter was sent to Auchincloss' Newton office.

Federal authorities are investigating after they say numerous letters with a “suspicious” substance were mailed to congressional and election offices nationwide and have urged recipients to treat the mailings as “potentially hazardous.”

Experts say even if nothing harmful is found, authorities need to treat the risk seriously.

"The one time that you that you're wrong, innocent bystanders could end up deceased or very sick," said Timothy Gallagher, former director of the FBI's New Jersey field office.

These are the first confirmed instances of the "suspicious" letters in Massachusetts.

The New Hampshire Attorney General's Office said Thursday that they had been contacted by the FBI and made aware that some offices in the Granite State had received suspicious letters. Some Connecticut lawmakers' offices were also targeted.

The investigation by the FBI, U.S. Postal Inspection Service and U.S. Capitol Police was first disclosed in a message from the Senate Sergeant at Arms obtained Thursday by NBC News. The notice, sent to Senate offices, said that law enforcement officials were working to intercept any additional letters, but “it is possible that some letters may reach their destinations.”

The FBI's Boston office said Thursday that it is investigating a series of suspicious mailings sent to various addresses nationwide along with the U.S. Postal Inspection Services. But they said they were not confirming specific instances or offices targeted.

"We are also working with our partners to identify the individual or individuals responsible for the letters. The FBI and the U.S. Postal Inspection Service will continue to safeguard the public and secure elections for American citizens," they said.

The Associated Press contributed to this report.