The families of Brian McKinney and John McClory, both Catholics who were seized by terrorists in May 1978, were said to be "shattered" by the news.

Mr McKinney's mother Margaret said: "I'll never lose hope. We'll find him some day."

Royal Ulster Constabulary officers spent four days digging up concrete steps at Glen Colin Way, Glen Road, near the Lenadoon Housing Estate, after an anonymous caller tipped them off.

Burial arrangements

Excavation teams are expected to return in the New Year.

A spokesman for the RUC said: "We share the families' disappointment that the information we were acting upon did not lead to the recovery of the remains."

There are 14 victims of IRA executions whose bodies have never been recovered and pressure is increasing on paramilitary leaders to help recover them and end their families' suffering.

Mrs McKinney had begun to make arrangements for her son's burial when she received the news that he had not been found.

'Intense work'

"I am certain the bodies will be found. I just hope it is soon.

"It's wonderful something is being done. So many years have passed when nothing was done, but this work is so intense and it does make a difference," she said.

"This has really shattered me, but if I could stand it up to the time when Brian was taken, then I can bear up to this. I just won't give up hope."

The job of finding bodies has been complicated by the length of time that has elapsed since the killings, the fact that many of those involved may themselves be dead and allegations that individuals sent to dispose of corpses were often drunk at the time.