Relatives fear it may be a fresh attempt to cover up the murders of 31 people who died in the car bomb detonated by the Real IRA in 1998.

They say the memorial stone, bearing the words which describe what happened in the Omagh bomb, was taken out of the garden by building contractors, leaving a hole in the ground.

The garden at Drumragh Avenue was closed by Omagh District Council as work to create the new Garden of Light is to start.

There has been controversy over the wording of the new memorial, to be in place for the 10th anniversary.

Michael Gallagher, chairman of Omagh Support and Self Help Group, has campaigned for words on the new memorial to state that 31 people from three nations died in the attack by dissidents – and to reflect the "truth".

Mr Gallagher told the News Letter: "Our concern is that the stone will not be returned to the new site."

The council is storing the stone for "safekeeping".

"But it is evident it will never see the light of day," Mr Gallagher said.

His letter from the council states that the nature and location of the new memorial is being considered by the independent facilitation team and a report is expected.

He said that in the letter the council's chief executive Danny McSorely said: "I'm sure you will agree that a decision on the future location of the memorial stone should only be taken in context of their report."

Mr Gallagher said: "What is alarming is that if the wording on the stone does not suit the committee we fear it will not go back into the garden," he said.

An Omagh District Council spokesman said bereaved families had advance notice of the garden closure to allow visits.

He said the independent facilitation team is meeting victims' families and those injured or traumatised by the atrocity to discuss views on narrative and location.

"A decision on the future of the existing memorial stone will be taken in the context of that report and recommendations which will have been reached in full knowledge of the range of views which exist among victims of the Omagh bomb of August 15,1998," he said.

The plan drawings for the new memorial do not have provisions for the old stone to be returned, he said.

"The whole point of the facilitation process is to decide on where the words will go and what they will be," he said.

However, Mr Gallagher said: "If the stone is not returned it will be obvious that it was the cause of embarrassment.

"If the stone is not returned it will be an attempt to cover up what happened at the hands of republicans in Omagh.

"Rest assurred the dead will be remembered in a fitting way and we will not allow the truth to be covered up."

The new memorial, designed by architect Desmond Fitzgerald and artist Sean Hillen, includes a glass pillar and cut glass heart at the Omagh bomb site which will be linked to the memorial garden by a pathway of sunlight reflected by mirrors for each of the 31 lives lost.