FBI spokesperson Martin Feely said agents were “carrying out a law enforcement action in connection with an ongoing investigation.”

Along with the union’s Manhattan headquarters, agents also searched union president Ed Mullins’ home in Port Washington, Long Island, Feely said.

Messages seeking comment were left with Mullins and the union.

Mullins, who is also a police sergeant, is in the middle of department disciplinary proceedings for tweeting NYPD paperwork last year pertaining to the arrest of Mayor Bill de Blasio’s daughter during protests over the Minneapolis police killing of George Floyd.

Mullins’ department trial began last month but was postponed indefinitely after one of his lawyers suffered a medical emergency.

Mullins’ lawyer denies he violated department guidelines, arguing paperwork with Chiara de Blasio’s personal identifying information, such as her date of birth and address, was already posted online.

Mullins is also suing the department, claiming they were trying to muzzle him by grilling him and recommending disciplinary action over his online missives.

Asked about the raid Tuesday, Mayor de Blasio told reporters he didn’t have enough information to comment.

“I think he’s been a divisive voice,” de Blasio said of Mullins. “But that doesn’t cause me to feel anything in this situation because I don’t know what’s happening. All I hear is an FBI raid. I don’t know the specifics, I don’t know who it’s directed at. I want to really hear the details before I comment further.”

The Sergeants Benevolent Association represents about 13,000 active and retired New York police sergeants, a rank above police officer and detective but below captain and lieutenant.

Under Mullins’ nearly two decades of leadership, the union has fought for better pay ” with contracts resulting in pay increases of 40 per cent” and staked a prominent position in the anti-reform movement.

Along with Mullins’ periodic appearances on cable networks like Fox News and Newsmax “including one in which he was pictured in front of a QAnon mug” perhaps the union’s most powerful megaphone is its 45,000-follower Twitter account, which Mullins runs himself, often to fiery effect.

In 2018, amid a rash of incidents in which police officers were doused with water, Mullins suggested it was time for then-Commissioner James O’Neill and Chief of Department Terence Monahan to “consider another profession” and tweeted that “O’KNEEL must go!”

O’Neill retorted that Mullins was “a bit of a keyboard gangster” who seldom showed up to department functions.

Last year, Mullins came under fire for tweets calling the city’s former Health Commissioner, Dr. Oxiris Barbot, and US Rep. Ritchie Torres a “first-class whore.”

Mullins was upset over reports Barbot refused to give face masks to police in the early days of the pandemic and angry with Torres’ calls for an investigation into a potential police work slowdown in September 2020.

Torres, who is gay, denounced Mullins’ tweet as homophobic.

On Tuesday, Torres referenced that tweet in reacting to the news of the raid, writing: “Ed Mullins, who famously called me a first-class whore’ for daring to ask questions about the @SBANYPD, just got a first-class raid from the FBI.”

In 2019, it wasn’t tweeted that got Mullins in trouble, but rather comments he made in a radio interview suggesting that slain Barnard College student Tessa Majors had gone to the park where she was killed to buy marijuana. Police later arrested three teens, saying she’d been stabbed during an attempted robbery.

Majors’ family called Mullins’ remarks on the radio show “deeply inappropriate” victim blaming and urged him “not to engage in such irresponsible public speculation.”