Elizabeth Warren

Federal prosecutors investigating a threat made against Sen. Elizabeth Warren are seeking to collect testimonies from members of her staff — a process complicated by the government’s separation of powers.

A person had contacted Warren’s office and threatened the senator, according to Senate Majority Leader John Thune, who submitted a resolution Thursday on behalf of himself and Senate Minority Leader Chuck Schumer authorizing members of Warren’s staff to provide testimony for the investigation.

Spokespersons working in the offices of Schumer, Thune and Warren did not respond to questions about the resolution and incident.

A spokesperson for the U.S. Attorney’s Office for Massachusetts declined to comment.

While Warren wants to cooperate by making her staff available, according to the Congressional Record, the U.S. Attorney’s Office for the District of Massachusetts first needed to have the matter go before the Senate.

The Senate must give permission before evidence under its control is used in administrative or judicial proceedings, according to the resolution that passed unanimously.

In addition to assisting with the investigation, the resolution authorizes members of Warren’s staff to testify in “any future legal proceedings in this matter.”