Irish property tycoon Kevin McGeever, who has reappeared after being kidnapped eight months ago, claims he was held in a shipping container and starved by his captors.
McGeever, 68, is believed to have told police he was given just one ham sandwich per day.
He also told them how he paid €80,000 (£69,000) in ransom money to his captors, but they had originally demanded €10 million (£8.6 million).
McGeever was found emaciated and confused wandering down a country lane in Ballinamore in County Leitrim last week.
He was taken to a police station by local resident Catherine Vallely and her partner Peter Rehill, where he told officers he had been held captive since June last year.
Reports said McGeever had the word 'thief' carved into his forehead, and he himself has suggested the Russian mafia was involved in his kidnap.
During the period in which he was missing, McGeever lost around five stone. He was found with a long beard, long fingernails and without shoes after being thrown from a van.
McGeever claims to have been abducted by three armed and masked men last May. He was bound, gagged and hooded before being transported for two days in a van. He was then walked downhill and put inside a container.
A source close to McGeever's family told the Irish Independent: "When he had the hood taken off he realised he was in a shipping container. On the walls there were pictures of other men with their names written on them."
McGeever was told that the men in these pictures were dead and that he "would be next".
Every day, at around 10pm, he was given just one ham sandwich and a drink of water. He was given a bucket to use as a toilet and was regularly beaten.
McGeever could only tell day from night through a crack of light that served as a ventilation hole.
The source added that his captors never spoke to him: "He has said that if it wasn't for his spirituality he would not have survived. He is in a terrible way over all of this.
"He cannot understand what happened and why."
Police are now looking into text messages sent to McGeever's partner, Siobhan O'Callaghan, just after he went missing reassuring her he was well. The messages were sent from mobile networks in the UK and Germany.
McGeever is currently being treated in Mullingar General Hospital for malnutrition and dehydration. It is thought he will be well enough to be released by the middle of the week.