CONCORD — Employees of the New Hampshire Democratic Party were let back into their North State Street headquarters after Concord police said testing of a suspicious package delivered by mail there Monday contained “no bio hazardous substances.”

Concord police said local state and federal authorities continue to investigate, and anyone with information is urged to contact Concord police Lt. Sean Ford at 230-3728 or the Concord Regional Crimeline at 226-3100.

“At this time no bio hazardous substances have been detected and there is no public safety concern,” Ford said in a statement.

Attorney General Gordon J. MacDonald along with the offices of Gov. Chris Sununu and the Merrimack County attorney were briefed on the matter.

Concord police and fire had first responded Monday at 5:09 p.m. after an employee with the party opened an envelope and told authorities some of what was in the envelope “may have gone airborne.”

State police and the Central New Hampshire Hazardous Materials team were also called in to assist, collect evidence and turn over material to the public health laboratory for testing.

There were no injuries reported but two staff members were evaluated as as a precautionary measure, officials said.

“Our immense thanks goes out to the Concord Police Department, the Concord Fire Department, and the New Hampshire State Police, whose swift and thorough response was a comfort to all NHDP staff members,” said Raymond Buckley, New Hampshire Democratic Party chairman, said.

“While we are relieved the package did not pose a direct threat to our staff members, it served as an important reminder that the toxic and hateful words spewed in our current political environment have ramifications far beyond scoring political points. Working to support members of the Democratic Party should never come with a fear of attack, and steps must be made to make our political discourse more tolerant and civil. Many thanks to all who reached out with support during the last 24 hours, it is deeply appreciated.”