The 19-year-old girl and a 20-year-old man were taken to hospital from RockNess yesterday morning, just hours after a 19-year-old man from Edinburgh died when he is thought to have taken drugs at the event on the banks of Loch Ness over the weekend.
The tragic teenager became ill on Saturday night and was treated at the scene before being taken to Raigmore Hospital, Inverness where medics battled in vain to save him.
He lost his fight for life early yesterday.
A police spokesman said: "Early indications are that the man may have consumed drugs."
Officers are thought to be probing the use of a 'legal high' substance known as benzo fury, a drug which is thought to have been consumed by some at the event near Inverness.
Event commander Superintendent Stevie Mackay said: "Taking drugs or any medicines, which you have not been prescribed is an extremely risky thing to do.
"People may think that legal highs are safe, because they are not classed as a controlled drug, but they are extremely dangerous."
Police at the event carried out drug searches using sniffer dogs.
Meanwhile, two men killed in an A9 road crash involving a van and a bus taking people to the festival on Friday were from the Glasgow area.
Decorators Mark McFarlane, 38, and Barry Murray, 28 died instantly in the smash which resulted in the seriously injured bus driver being airlifted to Glasgow's Southern General Hospital.