A recording of the moment paramedics first announced Michael Jackson's death has been found online.

The voice on the tape - which is believed to feature a Los Angeles Fire Department medical calling ahead to the UCLA Hospital in Santa Monica - could even be used as new evidence in the trial against the star's personal physician Dr. Conrad Murray who has been charged with involuntary manslaughter.

The voice is heard saying: "Patient is Michael Jackson, the pop star singer. No pulse, no breathing. Unresponsive. Tried to resuscitate him. Unsuccessful. We've done everything we can. We should be there in five minutes. It doesn't look good. It doesn't look good."

If the recording is genuine then it would be crucial to the trial into Michael's death because it contradicts the timeline of events previously stated by Dr. Murray who said the 50-year-old music legend still had a pulse and was warm when he put him in the ambulance.

If the tape is used, prosecutors would argue Dr. Murray, 56, actually left Michael for more than an hour after giving him the powerful sedative Propofol, making his actions careless.

The tape, which emerged on the ambulance workers' web forum, is thought to be the first time the announcement was made that Michael was dead on June 25 last year, although authorities do not yet know whether it is genuine.

An LAFD spokesman said: "I couldn't confirm that it is one of our workers. It could be. They refer to 'pop star Michael Jackson' but it is not our practice to name names."