Lt. Robert Sung, 50, and Detective Yatyu Yam, 37, are accused of intervening on several occasions when drug-using clubgoers, including at this Northern Boulevard karaoke bar, were arrested by fellow officers at the nightclubs they were protecting, according to court documents and sources. View Full Caption DNAinfo/Katie Honan

QUEENS — Nearly two dozen NYPD officers are under investigation as a result of the recent arrest of a lieutenant and a detective involved in a protection racket for karaoke clubs and bar owners in Flushing, DNAinfo New York has learned.

Two captains, three lieutenants, three sergeants, three detectives and 12 police officers are now under a cloud in the aftermath of a two-year investigation that ended in December with the arrest of Lt. Robert Sung and Detective Yatyu Yam of the 109th Precinct, according to confidential NYPD documents obtained by DNAinfo's “On the Inside.”

READ MORE: NYPD Officers Took Bribes to Protect Karaoke Bars From Police Raids: DA

The internal records include the names, photos and possible violations of department or criminal regulations each of 23 officers may have committed, but provide few specifics.

Sources say some allegations come from Yam, 35, who was arrested by Internal Affairs Bureau investigators and prosecutors from the Queens District Attorney’s Office, and taken to a secret location in a hotel where he was debriefed over two days.

The strongest evidence, however, was captured on recordings and surveillance tapes that shows Sung and Yam convincing fellow officers not to raid the clubs they were protecting or to free customers being handcuffed for using drugs there.

Sources say that instead of listening to Sung and Yam, the officers should have notified IAB or their supervisors about possible corruption, as is required by NYPD policies.

The most serious allegations involve: a captain who allegedly “associated with a narcotics user;" a lieutenant who hung out “with a known criminal;” a sergeant and a detective who allegedly “misused department computers;” and a sergeant, a detective and an officer who allegedly took a bribe, according to the documents.

Others are suspected of failing to take police action or report possible wrongdoing to higher-ups or Internal Affairs.

DNAinfo New York is withholding the officers’ names because they have yet to be charged with any offense. Many have already been grilled by IAB and deny any wrongdoing, sources say.

Court documents, however, show at least one officer was secretly recording his colleagues and cooperating with investigators during the criminal probe.

So far, about a half-dozen officers have already been stripped of their badges and guns and placed on modified duty.

An NYPD spokesman, citing an "ongoing investigation," declined to discuss the case.

According to the confidential IAB report, more than a dozen of the officers — including several detectives — worked at the 109th Precinct during the two-year criminal probe of Sung and Yam.

Three of those officers were transferred to commands in Manhattan, The Bronx, and Brooklyn just a week ago in a continuing shakeup of 109th Precinct personnel.

Yam, a 10-year NYPD veteran, was allegedly in cahoots with the owners of as many as eight popular karaoke bars in Flushing, and was so close to the owner of two nightspots that the owner was invited to backyard barbecues at the detective's home, where he gave Yam a monthly $2,000 payoff for protecting his karaoke clubs.

In all, Yam allegedly collected tens of thousands of dollars in payoffs tipping off owners about possible raids and for ordering fellow cops to free suspects they grabbed during raids that he could not prevent, court documents allege.

"At least for now,” one source told "On the Inside," it is likely any future charges will be leveled departmentally by the NYPD, although additional arrests cannot be ruled out because "this appears to be the tip of an iceberg of what's been going on."

Meanwhile, Sung, who is 50 with more than 20 years in the department, was terminated by the NYPD for refusing to be interrogated by Internal Affairs Bureau while under suspension.

His lawyer, Marvyn Kornberg, would say only that Sung “was not fired over any charges involved in the criminal case.” Sung faces up to seven years in prison, however, if convicted of taking bribes.

Yam’s lawyer, Jeffrey Lichtman, said he is “attempting to work out (the case) and hopes to resolve the matter amicably."