Police Scotland is investigating the deaths of two teenagers at T in the Park.
It is understood one female and one male have died.
The deaths are not thought to be related and they are being treated as unexplained.
Campers started arriving at the Strathallan site in Perthshire on Thursday and tens of thousands of people are expected to attend over the course of the weekend.
A police statement said: “Police Scotland can confirm we are investigating reports of the death of a female and the separate death of a male at T in thePark.
“The deaths are unexplained at this time and work is ongoing to establish the exact circumstances surrounding both.”
Festival organiser Geoff Ellis expressed his sorrow at the news.
“We are shocked and saddened by today’s news and our thoughts are with the families and friends at this time,” he said.
“We are offering our full support and assistance.”
There are unconfirmed reports that both of the deaths are drug related.
UPDATE: I'm told the two people dead at T in the Park are teenagers and it is drugs related. Major investigation underway.
— Connor Gillies (@ConnorGillies) July 8, 2016
Politicians are already calling for a prompt investigation into the circumstances surrounding the deaths.
Scottish Conservative MSP for Mid Scotland and Fife Liz Smith said: “This is tragic news and I am sure I echo the sentiments of everyone when we send condolences to the families involved and, indeed, to the organisers of T in the Park who have worked hard this year to overcome last year’s concerns about public safety.
“Clearly, an investigation now has to take place and I hope this will be undertaken as quickly as possible. It is essential that police establish exactly what happened and why.”
Meanwhile, Perthshire South & Kinross-shire MSP Roseanna Cunningham also expressed her sadness.
“I was shocked to hear of the deaths at T in the Park; what a dreadfully sad start to the festival weekend and my prayers are with the families, friends and loved ones of the people who have died.
“It is far too early to speculate about the circumstances behind the deaths but I know that every effort will be made to discover exactly what has happened.”
The event’s organisers issued a warning over the use of drugs on site just hours after details of the deaths emerged.
A drug amnesty was also set up.
T in the Park is Scotland’s biggest music festival, regularly attracting more than 80,000 revellers over the weekend.
This year marks the second time the event has been staged at Strathallan after moving from Balado in Kinross-shire in 2015.
Stone Roses are due to headline on Friday night.
Jamie XX, Disclosure and Courteeners are also scheduled to perform on Friday, before Calvin Harris and the Red Hot Chili Peppers headline on Saturday and Sunday.
(More to follow)
