Police detectives in Pittsburgh have been instructed to start bringing their riot gear to work over fears that President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE could soon fire special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE and set off widespread protests.

WTAE reporter Marcie Cipriani obtained emails sent to detectives in Pittsburgh warning them of a “potential large scale protest” in the city.

“There is a belief that President Trump will soon move to fire Special Prosecutor Mueller. This would result in a large protest within 24 hours of the firing,” the email read.

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Noting that the “protest would be semi-spontaneous and more than likely happen on short notice,” detectives were instructed to “bring a full uniform and any issued protective equipment (riot gear) with them to work until further notice.”

The email was signed by Commander Victor Joseph of Pittsburgh’s major crimes division.

SOURCE: This is the email sent to Pgh detectives this morning. I am working to get a response from the city as well as additional details on the potential protests. #WTAE pic.twitter.com/xtOuUc220p — Marcie Cipriani (@MCipriani_WTAE) April 18, 2018

Cipriani tweeted that Mayor Bill Peduto (D) told her police were preparing for possible protests over a potential Mueller firing, and that the email was a precautionary measure.

JUST IN: Just spoke to Mayor Bill Peduto, who confirms Pgh Police are preparing for possible protests. Peduto says the commander’s email asking for detectives to bring uniforms & riot gear starting tomorrow, is just precautionary #WTAE — Marcie Cipriani (@MCipriani_WTAE) April 18, 2018

Hundreds of thousands of Americans have signed up to protest if Trump does decide to fire Mueller.

Speculation has risen that Trump could move to fire Mueller. However, Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellPelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Senate GOP aims to confirm Trump court pick by Oct. 29: report Trump argues full Supreme Court needed to settle potential election disputes MORE (R-Ky.) said Tuesday that the Senate won't take up a measure to protect Mueller.

The White House said earlier this month that Trump believes he has the power to fire Mueller.