President Donald Trump has mulled firing the special counsel Robert Mueller, who is investigating Russian meddling in the 2016 election. REUTERS/Jonathan Ernst

Pittsburgh police have alerted detectives and officers of potential protests if Special Counsel Robert Mueller is fired by President Donald Trump.

The police have been told to be in uniform and have riot gear ready beginning Thursday.

The Pittsburgh police department has reportedly alerted its officers and detectives of potential protests if President Donald Trump fires the special counsel Robert Mueller, and is preparing for riots if he does.

Pittsburgh police sent an email on Wednesday telling officers and detectives that the department has "received information of a potential large protest in the Central Business District" that would be a response to Trump firing Mueller, according to Marcie Cipriani of WTAE-TV, the ABC station in Pittsburgh.

The police department also warned that the protests could happen in as little as 24 hours after the potential termination. The police have been told to be in uniform and have riot gear ready beginning on Thursday until further notice.

Pittsburgh Mayor Bill Peduto confirmed the email that the city's police force is preparing for protests, according to Cipriani.

"You want to be precautionary, especially on something that is unprecedented in American history," Peduto told her.

The warning comes at a time when there are growing concerns that Trump could look to undermine or completely shut down special counsel Robert Mueller's investigation into Russian meddling in the 2016 US election and the Trump campaign's possible ties to Russia. Trump has recently ramped up his public and private attacks on Mueller's probe.

Many Republicans and Democrats have urged the president not to fire Mueller or Deputy Attorney General Rod Rosenstein, who is overseeing the special counsel's investigation on behalf of the Justice Department. Lawmakers have told Trump to allow the investigation to run its course and not to impede, as it could lead to a constitutional crisis and a potential impeachment.

Some lawmakers have proposed legislation to protect Mueller and the investigation from being disbanded, but GOP leadership has indicated it thinks that's unnecessary.

On Tuesday, Senate Majority Leader Mitch McConnell said he wouldn't let such a bill make it to the Senate floor for debate.

There have been two reported instances when Trump apparently considered firing Mueller:

In May 2017, shortly after Mueller's appointment and following then-FBI director James Comey's firing. White House general counsel Donald McGahn reportedly threatened to resign if Trump demanded that he carry out the order, and Trump backed off. In December 2017, after Trump caught wind of reports that Mueller was seeking information on his family's personal business dealings with Deutsche Bank. Mueller's team notified Trump associates at the time that the reports were untrue.

Trump has publicly said he doesn't plan on firing Mueller, because if he wanted to, "he would have" already.

NOW WATCH: Popular Videos from Insider Inc.