Two men remain in critical condition in Waterford General Hospital today after taking drugs at the house party in the town last weekend.
John Grey (23), from Ballybeg, and Kevin Doyle (21), from the Viewmount estate, are on life-support machines in the intensive-care unit, a spokeswoman for the hospital said.
A third man who was also treated at the hospital after falling ill at the party was discharged from hospital yesterday.
Gardaí say their investigation into the incident is ongoing and they are continuing to question people who attended the birthday party at Ballybeg Square last Saturday night.
Earlier this week gardaí received the result of tests on a drugs cocktail that left the two young men critically ill and 13 other people requiring medical attention.
However, Superintendent Dave Sheehan who is heading up the inquiry, declined to reveal the type of substance recovered from the house at Ballybeg Square but insisted it was not toxic.
"To allay the fears of the public out there, because I do know there were a lot of fears around the place, I can say there was no horse tranquilliser in this substance," he said earlier this week.
Supt Sheehan said the possibility the men had taken an overdose was being examined. But, he said: "It possibly was more to do with the quantity [taken] as opposed to anything in it that was taken".