THE mystery behind a viral clip which featured a strange voice whispering about "irreversible death" during ITV's coverage of the Queen's funeral has been solved.

The 21-second clip of the Queen's coffin travelling between Westminster Abbey and St George's Chapel in Windsor racked up over 1.5 million views on Twitter.

The footage, taken from the air, begins silently but after a few seconds a hoarse female voice can be heard whispering, "that death is irreversible and the fact that she's ..." before a male presenter can be heard talking.

READ MORE: Patrick Harvie: People stop me on the street and say well done for my speech to King Charles

Social media users theorised that the last word heard from the woman was "trapped" OR "travelling", but the audio is difficult to make out as there is a ringing noise accompanying the clip. 

The second voice cuts out again and then the male presenter says: "As you can see here in London it is a lovely day and as a hearse heads out into West London..."

Social media users were baffled by the clip and began to share jokes and theories about it.

One wrote: "This is one of the oddest things I've heard in a while..."

Another joked: "Her death is irreversible! Who knew?"

One added: "Whatever this is I’m a truther now."

While another, sharing a gif of Princess Diana, said simply: "Spooky."

READ MORE: 'F*** The King' graffiti appears on Rangers pub in Glasgow

Other social media users joked that the voice was a ghost or a supernatural being with many demanding an explanation.

Another Twitter user said: "Well, this is… unnerving."

While one added: "Why does this sound like those creepy 'is that a voice' recordings from haunted sites."

While ITV declined to comment on the clip, The National understands that the sound was a guest of the broadcaster whose voice was picked up by a presenter's microphone.