(CBS) A tape of emergency radio transmissions on Sept. 11 shows that firefighters reached the burning 78th floor of the south tower where the jetliner sliced through, nearly 30 floors higher than officials had estimated.

Four people who have listened to the tape said at least two firefighters reached the crash site and were helping the injured, The New York Times reported for Sunday editions.

The 78-minute tape was found in the rubble months ago but was not played until fire officials signed a confidentiality agreement.

The agreement was requested because the tape may be used as evidence in the trial of Zacarias Moussaoui, accused of conspiracy in the Sept. 11 attacks. Moussaoui, who faces the death penalty, has said he is a loyal member of al Qaeda but denies a role in Sept. 11.

Officials had thought that firefighters had not climbed higher than the 50th floor in either tower. United Flight 175 crashed into the south tower between the 78th and 84th floors. American Airlines Flight 11 sliced through the north tower near the 91st floor.

Most of the transmissions on the tape came from the south tower.

The fire department has identified the voices of at least 16 firefighters on the recording, and the families were invited to listen to the tape Friday after signing confidentiality agreements.

Debbie Palmer, whose husband, Battalion Chief Orio Palmer, can be heard on the tape, would not break her agreement but said the recording gave her some peace about her husband's last moments.

``I didn't hear fear, I didn't hear panic,'' she told The Times. ``When the tape is made public to the world, people will hear that they all went about their jobs without fear, and selflessly.''