Gun arrests at the north Bronx’s 52nd Precinct more than tripled between 2016 and 2017.

Prosecutors are investigating whether cops in a Bronx precinct that has been praised for its surge in gun arrests broke the law to make some of those busts, the Daily News has learned.

The months-long probe by the Bronx district attorney’s office has led to some gun cases being shot to bits.

Some cops could be indicted for perjury and official misconduct, police sources said. The NYPD may transfer others or bring them up on departmental charges, the sources said.

“Our Public Integrity Bureau is investigating the allegations,” DA spokeswoman Patrice O’Shaughnessy confirmed.

The investigation focuses on the tactics cops used to recover guns. It has already had an impact on several criminal cases, with prosecutors dismissing charges against defendants or offering sweetheart plea deals.

“All of a sudden we were seeing heavy cases, felony cases, and right away the DA’s office is offering pleas to misdemeanors,” said a defense lawyer who asked not to be identified. “We knew something was up.”

Sources said investigators are looking into whether officers dangled deals to suspects — particularly those busted for drugs. They want to see if cops asked for their cooperation in finding guns in exchange for lesser charges — and no gun arrest.

In some cases, sources said, suspects may have taken the bait, allowing police to search for and recover a gun, sometimes in the suspect’s house. But rather than stick to the deal, the cops reneged — and charged the suspects with gun possession, the source said.

The DA is also looking into whether police obtained consent for searches in some cases, sources said.

The NYPD declined to comment on the probe.

Roy Richter, the head of the Captains Endowment Association, defended the precinct’s commanding officer, Deputy Inspector Peter Fiorillo.

“The officers in the 52nd Precinct are making solid gun arrests based upon observation and outstanding police work,” Richter said.

The defense lawyer said police are allowed to lie to suspects and that tricking one into giving up a gun is nothing new. But the problem is the initial arrests, the lawyer said. “They’re not justified arrests — but then once you’re in custody they try to get a gun,” the lawyer said.

The 52nd Precinct has seen a spike in gun arrests and has been praised at the NYPD’s CompStat meetings, where brass grill commanding officers about crime.

In fact, by late June, gun arrests at the north Bronx command more than tripled — from 27 during the first half of 2016 to 84 during the corresponding period last year.

The startling spike fizzled out in the second half of the year when the DA’s office launched its probe. The precinct made 139 gun collars in 2017, an increase of 56% from the 89 in 2016.

The Legal Aid Society said the probe matches what it has heard from suspects who have complained about alleged officer misconduct in the 52nd Precinct.

“We’ve noticed a consistent pattern of complaints involving officers fabricating consent, harassing people repeatedly in their homes, and unlawfully stopping and searching people in an attempt to generate information on unrelated cases,” said Peter Jones, who heads the group’s Bronx criminal defense office.

“We’ll continue to monitor incidents as they arise and push to litigate these and all cases involving police misconduct.”