One man remains in a critical condition.
A 23-year-old man is in a critical condition after possibly taking fake Xanax tablets at a homeless hostel in Tullamore.
Two women also staying at the premises died in the last 48 hours.
The two victims have since been named. 44-year-old Angeria Kelly from Portlaoise died at Clonamore House on Sunday while less than 24 hours later, 19-year-old Amy Mannix from Kerry died at the same premises.
While emergency services were still at the hostel, a 23-year-old man became unresponsive and is now in a critical condition in hospital.
A fourth person staying at the hostel, a 32-year-old man, is also unwell, but his condition is not believed to be life-threatening.
Gardaí are awaiting toxicology reports but one line of inquiry is that the victims took fake Xanax tablets.
Officers are also investigating whether the death of a 30-year-old man at a different hostel in Tullamore on Thursday could be connected to this investigation.
