This article was reproduced with the kind permission
of the British Broadcasting Corporation
18 November 2007, 18:59 GMT
It is understood Mr McElhill is suspected of starting a fire in his Omagh home which killed himself, his partner and their five children.
His relatives said they were still grieving after Tuesday's fire.
Meanwhile, social services have refused to comment on reports that a child was recently placed in his care despite him being on the sex offenders register.
It is understood police had the child removed in recent weeks from the house at Lammy Cresent.
Police said they would not comment on this, as their murder inquiry relating to the fire was continuing.
All seven deaths are being treated by detectives as murder.
Police said petrol had been scattered around the house and it had been set alight. The family died of smoke inhalation.
Mr McElhill, 39, died in the fire along with his partner Lorraine McGovern, 30, and their five children, Caroline, 13, Sean, 7, Bellina, 4, Clodagh, 19 months and James, who was nine months old.