Police and the Criminal Assets Bureau began an intensive search of the large Dublin property this week, The Irish Times reported. The house and grounds were sold last year after Tom McFeely was declared bankrupt.
By Thursday, 200,000 euros (almost $270,000) had been discovered, Prime Minister Enda Kenny said. McFeely during bankruptcy proceedings last year said he was almost broke.
A plumber found a stash of 50 euro ($67) bills hidden in a bathroom last week. He reported the find to the house's new owners and they got in touch with police.
McFeely, a militant in the Provisional IRA, spent years in Belfast's notorious Maze Prison in Northern Ireland before being released in 1989. He survived the 1980 hunger strike that killed 10 prisoners.
Once he was free, McFeely became a construction worker and then a developer. He was involved with the Priory Hall development in Dublin, which was emptied in 2011 because of safety concerns.
Kenny said the National Assets Management Agency would take control of the new money, using it to pay McFeely's creditors.
"I think all of that smacks of what happened during the so-called tiger years when you had prolificacy and greed and money sloshing around in so many places," Kenny said.