Four New Jersey members of Congress received suspicious mail or packages on Friday as federal authorities continue to investigate a nationwide wave of letters sent to lawmakers and election officials, some containing unidentified substances.

U.S. Reps. Bonnie Watson Coleman, Analilia Mejia, Rob Menendez and Frank Pallone, all Democrats, were among those targeted.

Watson Coleman, who represents New Jersey’s 12th Congressional District, said her district office was closed Friday after receiving a suspicious package. Ewing Township police responded, and a New Jersey State Police hazardous materials team seized the package.

Menendez, who represents the 8th Congressional District, said his Jersey City office temporarily closed after receiving a suspicious package. The substance was determined to be nonhazardous, and the office subsequently reopened, he said.

Pallone, whose 6th Congressional District includes parts of Monmouth and Middlesex counties, also received a suspicious package containing a white powder, according to a spokesperson for his office. The substance was tested and found to be nonhazardous. The letter was postmarked in Texas but carried a New York return address, the spokesperson said.

Mejia, who represents the 11th Congressional District, said a postal worker flagged a suspicious letter before it reached her office. She described the letter as containing an unidentified substance and characterized the incident as an apparent attempt to harm her and her staff.

The incidents come amid a broader investigation into suspicious mailings sent to congressional offices and state election officials across the country.

The FBI and U.S. Postal Inspection Service are investigating the mailings, some of which contained unknown substances. The U.S. Capitol Police and other law enforcement agencies are also involved in responding to the incidents. Authorities have urged recipients to treat suspicious mail as potentially hazardous while the investigation continues.

Federal officials have not publicly identified those responsible for the mailings or established whether all of the incidents are connected. Testing in several cases has found the substances to be harmless.

The investigation comes less than three weeks before the Nov. 3 midterm elections, as officials work to protect lawmakers, election workers and government offices from potential threats