Health chiefs have launched an investigation following the deaths of two patients at different hospitals.
A patient receiving treatment at the acute mental health unit of Tallaght Hospital, Dublin, passed away on Monday.
A separate death occurred on the other side of the country at Kerry General Hospital in Tralee on the same day.
The patient at Kerry had also been receiving psychiatric treatment.
A spokesman for the Health Service Executive (HSE), which announced it is to carry out a review following the deaths, insisted the incidents were completely separate.
"The HSE would extend its sympathies to the families and is offering support to everyone affected," said the spokesman.
"An immediate review has begun."