Boxer Michael O'Reilly has been suspended from the Olympics after failing a doping test in a huge blow to Team Ireland at this year's Games.
The 23-year-old, who has already been embroiled in separate controversies, was tested by Irish authorities in the run-up to his departure for Rio on July 19.
News that he failed the test emerged just as the draw for the competition was getting underway in Rio.
O'Reilly, who boxes out of Portlaoise, is understood to be planning a challenge against the results.
Last night he indicated that he plans to fight as normal - in the middleweight division - later in the month.
In a tweet posted a short time after the failed test emerged he said: "Box on the 12th in the last 16 against the winner of Mexico or Iraq."
But sporting chiefs in Ireland refused to comment on this statement when contacted by the Herald.
Olympic champion Michael Carruth last night hit out at the results and slammed O'Reilly for the failed test. His reaction "was total disbelief", he said.
"I've no time for people who take drugs and try to - for the want of a better word - cheat. He should have known what he was taking," he said.
"Whatever punch I've ever been hit with in my life, it was nothing like today. We've never seen it coming, none of us. It's not in our sport really," he told the Herald.
"When have you ever heard of an Irish boxer failing a drugs test? For me, I'm in absolute shock and there is a big amount of disappointment. It's surreal, you could never fathom that.
"They're stringently tested and they know the dos and don'ts, and he's not exactly a young lad. If they feel anything they are putting in is untoward they can ask advice.
"If he didn't know what he was putting in, then he should have got it checked out - and if he did know, we have zero tolerance for people who take drugs.
"We want clean athletes. This is our sport and for this to happen is an absolute shock."
Mr Carruth said O'Reilly will now have a chance to have a second sample - a 'B sample' - tested, but said he will have to leave the Olympic Village if it also comes back positive for a performance enhancer.
O'Reilly has picked up several medals since winning his first at the European Championships at the age of 13.
Earlier this year, he qualified for the Olympics after the final qualifying tournament in Baku.
He won comfortably at the tournament and become the eighth and final Irish boxer to qualify for Rio.
In a statement, the Olympic Council of Ireland confirmed that Sport Ireland's Anti-Doping Agency had found that an Irish boxer tested positive for a banned substance.
However, it stressed that the test in question had not been taken in Rio, and related to an earlier test.
The OIC said that the athlete had been "provisionally suspended from competition and can take part in no sports activity - including training".
"The athlete will now decide whether to accept a sanction for a doping violation, to request that a B-sample be tested, or to appeal the provisional suspension," the OIC added.
Talented boxer O'Reilly was considered a key medal hope for Ireland at this year's games and has been making his name in the ring for a decade now.
The Herald spoke to O'Reilly in Dublin Airport before he flew to Brazil, and he said he and the team were "raring to go".
"I'm hoping to go and bring back a medal and I'm very, very confident that I will," he said.
"I think this is the strongest Olympic team that Ireland has ever had, so I'm hoping that we will all bring back a medal."
Asked about preparations in Rio ahead of the Games, O'Reilly insisted that it was all about "keeping safe".
"You just have to get on with it, keep yourself safe, and keep the hands wrapped up," he said.
The failed test has left Ireland's sporting ministers with red faces too, as the results emerged just 24 hours after they issued a statement which referenced doping.
"We look forward to supporting not just the athletes representing Ireland, but all of the clean athletes and competitors in Rio," Minister Shane Ross and Junior Minister Patrick O'Donovan said in a joint statement.
"We sincerely hope they will be performing in a doping-free environment. Illegal, performance-enhancing substances are, to our mind, the biggest threat to the integrity of sport and we welcome all initiatives and measures to protect that integrity and to protect clean athletes."