17-year-old Tory Johnston collapsed and died in Letterkenny hospital last Wednesday after feeling unwell at a nightclub earlier.
She had been enjoying a night out at Voodoo nightclub in the town, when she felt unwell and was taken to hospital. She was pronounced dead a short time later. A post-mortem examination failed to establish a cause of death.
Gardai are now asking anyone who may have been socialising with Tory to come forward and hand over photographs or video footage taken on the night in question.