NEW BRUNSWICK, N.J. » It’s an audiotape the New York Police Department hoped you would never hear.

A building superintendent at an apartment complex just off the Rutgers University campus called the New Brunswick Police 911 line in June 2009. He said his staff had been conducting a routine inspection and came across something suspicious.

"What’s suspicious?" the dispatcher asked.

"Suspicious in the sense that the apartment has about — has no furniture except two beds, has no clothing, has New York City Police Department radios."

"Really?" the dispatcher asked, her voice rising with surprise.

The caller, Salil Sheth, had stumbled upon one of the NYPD’s biggest secrets: a safe house, a place where undercover officers working well outside the department’s jurisdiction could lie low and coordinate surveillance. Since the Sept. 11, 2001, terror attacks, the NYPD, with training and guidance from the CIA, has monitored the activities of Muslims in New York and far beyond. Detectives infiltrated mosques, eavesdropped in cafes and kept tabs on Muslim student groups, including at Rutgers.

The NYPD kept files on innocent sermons, recorded the names of political organizers in police documents and built databases of where Muslims lived and shopped, even where they were likely to gather to watch sports. Out-of-state operations, like the one in New Brunswick, were one aspect of this larger intelligence-gathering effort. The Associated Press previously described the discovery of the NYPD inside the New Jersey apartment, but police now have released the tape of the 911 call and other materials after a legal fight.

"There’s computer hardware, software, you know, just laying around," the caller continued. "There’s pictures of terrorists. There’s pictures of our neighboring building that they have."

"In New Brunswick?" the dispatcher asked, sounding as confused as the caller.

The AP requested a copy of the 911 tape last year. Under pressure from the NYPD, the New Brunswick Police Department refused. After the AP sued, the city this week turned over the tape and emails that described the NYPD’s efforts to keep the recording a secret.

The call sent New Brunswick police and the FBI rushing to the apartment complex. Officers and agents were surprised at what they found. None had been told that the NYPD was in town.

At the NYPD, the bungled operation was an embarrassment. It made the department look amateurish and forced it to ask the FBI to return the department’s materials.

The emails highlight the sometimes convoluted arguments the NYPD has used to justify its out-of-state activities, which have been criticized by New Jersey Gov. Chris Christie and some members of Congress. The NYPD has infiltrated and photographed Muslim businesses and mosques in New Jersey, monitored the Internet postings of Muslim college students across the Northeast and traveled as far away as New Orleans to infiltrate and build files on liberal advocacy groups.

In February, NYPD’s deputy commissioner for legal matters, Andrew Schaffer, told reporters that detectives can operate outside New York because they aren’t conducting official police duties.

"They’re not acting as police officers in other jurisdictions," Schaffer said.

In trying to keep the 911 tape under wraps, however, the NYPD made no mention of the fact that its officers were not acting as police. In fact, Lt. Cmdr. William McGroarty and Assistant Chief Thomas Galati argued that releasing the recording would jeopardize investigations and endanger the people and buildings.

Further, the apartment, No. 1076, was rented by an undercover NYPD officer using a fake name that he was still using, New Brunswick attorneys told the AP.

"Such identification will place the safety of any officers identified, as well as the undercover operatives with whom they work, at risk," Galati wrote in a letter to New Brunswick.

The city deleted that name from the copy of the tape that it released.

Reached by phone Tuesday, McGroarty declined to discuss the New Brunswick operation. But the recording offers a glimpse inside the safe house: a small apartment with two computers, dozens of black plastic boxes and no furniture or clothes except one suit.

"And pictures of our neighboring buildings?" the dispatcher asked.

"Yes, the Matrix building," Sheth replied, referring to a local developer. "There’s pictures of terrorists. There’s literature on the Muslim religion."

New York authorities have encouraged people like Sheth to call 911. In its "Eight Signs of Terrorism," people are encouraged to call the police if they see evidence of surveillance, information gathering, suspicious activities or anything that looks out of place.

New York Mayor Michael Bloomberg has defended the police department’s right to go anywhere in the country in search of terrorists without telling local police. And New Jersey Attorney General Jeffrey Chiesa has said he’s seen no evidence that the NYPD’s efforts violated his state’s laws.

Muslim groups, however, have sued to shut down the NYPD programs. Civil rights lawyers have asked a federal judge to decide whether the spying violates federal rules that were set up to prevent a repeat of NYPD abuses of the 1950s, when police Red Squads spied on student groups and activists in search of communists.