Law enforcement sources told Hearst Connecticut newspapers it was unclear who the order was directed at. One said police officers who responded went into the building immediately while paramedics were told to wait for police clearance.
Adam Lanza, a 20-year-old alumnus of the school in Newtown, Conn., who had already killed his mother, shot 20 children and six teachers and staff before taking his own life Dec. 14.
On the tape, someone can be heard speaking from police headquarters.
"Wait until you go into the building," the voice says. "I'm not going to send them in yet."
The tapes show 911 dispatchers were overwhelmed by the huge number of calls about the shooting. One call went unanswered for 30 seconds while another caller, Rick Thorne, a Sandy Hook custodian, was disconnected.
A source told Hearst it was "weird" that Thorne was cut off.
"I'm standing in a corner not knowing what to do. I'm a custodian. The shootings happened 5 minutes ago," he said in one of his last calls.
Stephen J. Sedensky III, the state's attorney in Danbury, has been trying to keep the tapes from being publicly released during a court case now under way in New Britain, Hearst said.