Federal investigators probing Mayor Adams’ 2021 campaign are now zeroing in on a series of texts suggesting he helped fast-track the opening of the Turkish government’s new diplomatic headquarters in Manhattan, sources close to the case told The Post.

The September 2021 texts between Adams — who was then the Brooklyn borough president and Democratic mayoral nominee — and Turkish Consul General Reyhan Özgür and then-FDNY Commissioner Daniel Nigro were uncovered by FBI agents Monday after they seized Adams’ electronic devices.

The texts were described by sources to The Post.

Since Monday, the feds’ questions about the content on the devices – which included three cellphones and two iPads – have centered on these texts, sources said. 

However, the messages don’t appear to show any criminal activity beyond typical outreach that elected officials do on behalf of constituents, according to several sources briefed on the matter.

In a Sept. 5, 2021, text, Özgür informed Adams that construction was recently completed on the new Turkevi Center diplomatic headquarters, located on 46th Street and First Avenue across the street from the United Nations building, sources said.

However, Özgür noted that while the new HQ received needed approvals from the city Buildings Department to operate, it still had to secure a “temporary certificate of occupancy” from the Fire Department. He then asked Adams if he knew Nigro and could help.

Adams, according to sources, reached out to Nigro and asked him to look into the matter, but didn’t order him to do anything.

On Sept. 10, Nigro texted the future mayor, saying the needed approval would be good to go by the following Monday, or Sept. 13.

The 36-story Turkevi Center skyscraper celebrated its grand opening on Sept. 21, 2021. Besides being the New York home to the Turkish consulate, it also includes meeting space, commercial space and apartments.

Adams’ campaign declined to comment on the contents of the phone texts. Nigro and reps for the U.S. Attorney’s Office and FBI could not immediately be reached for comment Saturday night. 

Rubén Díaz Jr., a former state assemblyman and Bronx borough president, questioned whether the feds are firing blanks when told of the texts.

“I don’t think that should be a smoking gun,” he said. “I don’t see any issue at all. Every elected official makes calls to city agencies on behalf of entities, businesses and constituents. That is what we do.”

City Councilman Kevin Riley, another Bronx Democrat, agreed, saying he believed the mayor did nothing wrong.

“It’s not foreign for a [elected] member to reach out to a commissioner to see what they can do for constituents. It’s usually protocol,” Riley said.

Federal authorities are investigating whether the Turkish government or Turkish citizens illegally funneled donations to Adams’ campaign by using “straw donors,” a scheme where contributors listed in official records aren’t the actual source of funding and whether Adams did quid-pro-quo favors.

The investigators were specifically looking for proof that the campaign kicked back benefits to leaders and staffers at Brooklyn-based KSK Construction Group and Turkish officials.

The seizure of Adams’ electronic devices came four days after FBI agents armed with a warrant burst into the Brooklyn home of his lead campaign fundraiser, 25-year-old Brianna Suggs, seeking documents related to contributions to Adams’ 2021 campaign, as well as records of travel to Turkey by campaign employees that could reveal more about any ties to the Turkish government.

The raid prompted the mayor to cancel a meeting with White House officials about the Big Apple’s mounting migrant crisis. Adams – who has criticized President Biden’s lax border policies – flew back to New York City almost as soon as he had landed in D.C.

Adams’ campaign attorney Boyd Johnson said Friday the mayor was cooperating with federal authorities and had already reported that an internal review found “an individual had recently acted improperly.”

“In the spirit of transparency and cooperation, this behavior was immediately and proactively reported to investigators,” Johnson said.