By Rachel Clarke BBC News Online in Washington

Across the United States, people are steeling themselves for the second anniversary of the devastating attacks of 11 September 2001.

One officer issued a "mayday" just before the South Tower collapsed

But emotions have spilled over earlier than planned, with the release of transcripts from emergency calls and radio transmissions from inside the World Trade Center in New York after it was hit by hijacked planes.

But as relatives of those killed in the attacks praised or criticised the publication of some victims' last words, the sombre tone that characterises media coverage of 11 September was dominant.

Sally Regenhard, who lost her firefighter son on that day, said she wanted everything to be open to scrutiny so action could be taken to ensure greater safety in skyscrapers.

Leila Negron, whose husband was killed, said she cried after reading just three sentences and questioned why outsiders would want to know the details.

"I don't see anyone gaining anything out of it," she said.

But even if the media exercises restraint and shows sensitivity, there remains a huge interest in issues surrounding the 11 September attacks which affected the US population so deeply, even far away from where the planes struck in New York, Washington and Pennsylvania.

I've got five people here - we can't get out Man calling from the 90th floor, 11 September 2001 Excerpts from 9/11 tapes

Some is certainly idle curiosity, even though the events of the day are well known. But there also seems to be the desire to continue to find heroes amid such a huge tragedy which left a wound in the American psyche which has yet to heal.

Poignancy

There appear to be many horrific sights, sounds and thoughts captured in the words on the tapes. The fear and the shock comes through even though only transcripts, not the original tapes, have been released.

There are also passages which can seem mundane at first reading. But they take on poignancy with the hindsight and knowledge that nearly 3,000 people died in New York that day.

There is the Port Authority officer simply repeating his call-sign "82-Reynolds" as he tries to make contact with his control desk, unaware that the transmitter which should have carried his words had been knocked out by debris.

There is the measured request from a worker at the Windows on the World restaurant on the 106th floor. "We need direction as to where we need to direct our guests and our employees, as soon as possible."

And the reply from the Port Authority officer who took her call: "We're doing our best... we're trying to get up to you, dear."

Then there are the blunt statements from people who were yet to become victims such as a man on the 90th floor who asked for help and described his circumstances. "I've got five people here. We can't get out."

Elsewhere, a police officer called out "mayday" just moments before the South Tower collapsed.

'Painful reading'

Many of the voices on the tapes belonged to uniformed and civilian workers for the Port Authority of New York and New Jersey, which had to release the records after a Freedom of Information court challenge by the New York Times newspaper.

More than 25,000 people were evacuated safely

The Authority was unable to edit the 2,000 or so pages of transcripts of conversations it recorded from its own staff - who were the first officers to respond to the crisis - and from civilians caught in the Twin Towers.

Instead it had to urge reporters not to sensationalise the stories contained in about 260 hours of tapes.

Greg Trevor, a spokesman for the Port Authority and survivor of the attacks, said the transcripts made often painful reading, but demonstrated the bravery of rescuers who managed to evacuate about 25,000 people from the towers before they fell.