Two women, who are in a serious condition in hospital, may have become ill from using substances other than a contaminated batch of cannabis.
Fresh toxicology tests were under way last night to determine how they became critically ill.
But gardai now believe that cannabis may not have been a major factor in either case.
One of the women is now thought to have been inhaling a deodorant and this may have been more significant in creating her medical problems. Last night the woman’s condition at Our Lady of Lourdes Hospital in Drogheda had stabilised and she was no longer in a coma.
The second woman’s condition was also stabilising last night but she remained in a coma.
Fears that a contaminated batch of cannabis could have been responsible for their illnesses grew after initial toxicology tests on samples taken from the women at the hospital.
However, urine samples were sent yesterday to Beaumont Hospital in Dublin and then forwarded to the state laboratory and the forensic science laboratory at garda headquarters for further tests.
The fresh tests on the first woman, who is from Drogheda, showed that abusing the aerosol was the likely cause of the damage to her respiratory system.
She had been in Dublin on Tuesday and returned home to Drogheda that night. She was taken to the hospital at around 4.30am on Wednesday.
The second woman, who is from Kilsaran village, outside Castlebellingham, Co Louth, was taken to the hospital on Monday night. The additional tests on her samples had not been completed late last night. But it is believed substances other than cannabis are likely to have been responsible.
The two women, who are aged 24 and 22, are not connected. One of them is the mother of a young child.
By Tom Brady and Louise Hogan
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