NEW BRUNSWICK, N.J. (AP) — 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.