The Senate Sergeant-at-Arms Office warned chiefs of staff, staff directors, administrative managers and chief clerks to be on guard for mail that contained threats and suspicious powdery substances, according to an e-mail obtained by Roll Call.

A notice labeled “high” importance and forwarded from the office at 2:11 p.m. said the Senate Post Office on Tuesday found two such envelopes addressed to different Senators’ offices, both from the same sender.

“Initial tests of the substance were negative,” read the e-mail.

Offices were told to contact police immediately if they received mail addressed from the name Michael Taffinder from the Great Meadow Correctional Facility, a prison in Comstock, N.Y.

“These incidents are reminders that the entire Senate community needs to remain vigilant in handling mail, recognizing suspicious items, and knowing what immediate actions to employ if faced with suspicious mail in the office,” the e-mail said.