The search operation follows a report from a forensic scientist who told gardaí the cabin might have been used by Murphy if he had succeeded in his attempt to kill a woman before she was saved by two hunters.
In February 2000, Murphy abducted a young woman in Co Carlow and drove her to the Wicklow mountains where he repeatedly raped her.
He had bundled her into the boot of his car and intended to kill her when the hunters came across him near the cabin.
He was convicted of rape and attempted murder, serving 10 and a half years of a 15-year sentence before his release in August 2010.
Gardaí have always suspected Murphy had a remote location where he had intended to bring his victim and bury her.
The hunting cabin at Kilranelagh is 800 metres from the scene of the rape and about 7km from Murphy’s Baltinglass home.
Officers involved in Operation Trace — set up to investigate the unsolved cases of six missing women in Leinster between 1993 and 1998 — questioned him on the disappearances of three of the women: Jo Jo Dullard, Deirdre Jacob and Annie McCarrick.
However, gardaí have not been able to collect any evidence against him.
Murphy left the country after his release in 2010. Garda sources said the 46-year-old father of two was last seen in the Netherlands in December.
Gardaí yesterday confirmed the search of the cabin was linked to Operation Trace, and specifically to Murphy. The search is due to finish today.
“There is information coming in very regularly regarding Operation Trace,” a source said. “This is just one of a number of searches. The majority don’t turn up anything; some do.”
Gardaí used a JCB to remove the concrete floor of the cabin. The Garda Dog Unit and the Garda Technical Bureau are assisting the investigation, led by the Serious Crime Review Team, or cold case unit.
Barry Cummins, author of Missing and Without Trace, said people wondered where Murphy was going to bring his rape victim.
“One of the questions was what he intended to do with the body had he succeeded in murdering her, which by his own admission he had intended,” he said.
“Where was he going next with the body in the boot of the car? Where was he bringing her?”
DEIRDRE JACOB: Disappeared on July 28, 1998
JO JO DULLARD: Was last heard from on November 9, 1995
ANNIE McCARRICK: Vanished near Dublin mountains on March 26, 1993