Police are probing whether two Irish teenagers had their drinks spiked before dying within hours of each other while on holiday in Greece.
Andrew O'Donnell and Max Wall, both 18, had graduated from St Michael's College secondary school this year and travelled to the island of Ios with around 90 other classmates to celebrate the end of their exams.
During a night out on Saturday, Andrew became separated from a friend while walking back to their accommodation and was reported missing.
His body was found at around 9.20am the following day on rocks in a field, showing signs he had slipped and hit his head.
Max, who has a history of heart problems, collapsed near the island's port that afternoon after hearing about the death of his friend.
Despite the best efforts of medics, he was later pronounced dead in hospital.
Police are now investigating whether the two teenagers' drinks were tampered with, which may have contributed to both of their sudden deaths.
Konstantina Dimoglidou, a police spokeswoman, told the MailOnline : "While the injuries on {Andrew's] neck and head suggest at first glance that he strayed off course; that he tripped and fell, we are also exploring criminal negligence.
"The drinks that he and his classmates consumed may have been tampered with, leading him to the state he was in when he left the bar early Saturday to return to his hotel."
She added: "It remains to be seen whether some sort of induced substance may have contributed to both sudden deaths."
Local police previously confirmed that two inquiries are underway into the double deaths.
A regional police officer, speaking on condition of anonymity, said: "We understand that Max who was discovered in the port had a history of heart problems.
"Friends who were with him described him collapsing on hearing about Andrew. They were close.
"This is about as near as it gets to an ancient Greek tragedy."
It is understood that Andrew and Max's devastated parents have now travelled to Ios, to repatriate the bodies of the two teenagers.
Dozens of classmates in Greece are also reported to be travelling back to Ireland via Bristol.
Tributes have poured in for the two "bright, sporting and academic" young men.
St Michael's College in Dublin released a statement on Sunday about the death of Andrew before later confirming Max had also died.
Irish deputy premier and minister for foreign affairs Micheal Martin said a consular officer was on the ground on Ios supporting the families involved.
He described the teenagers' deaths as "devastating" and "every parent's nightmare".
Minister for Further Education Simon Harris said his thoughts were with Leaving Cert students on holiday in Greece who were "now encountering such shock and pain and grief".
On Monday, principal of St Michael's College Tim Kelleher said that representatives of the school's parent association had flown to the Greek island to support the families.
"We're absolutely devastated, the entire community is reeling with the news over the last 24 hours," he told RTE's Morning Ireland.
"Our deepest sympathies and condolences go to the bereaved families, some of the parents association reps have flown out to the island to give them some support in their time of need."
He described Andrew as a "fantastic young man, great sportsman, fantastic footballer" who was academically bright, and was looking forward to his holiday and to attending college.
"A very, very bright future," he said.
He described Max as "very bright", "passionate about rugby" and had "the world at his feet", saying he was "full of optimism and hope for the future".
Mr Kelleher added: "Unfortunately both families got the news yesterday that their future had been taken from them and we're obviously devastated for them, their family and friends, and we're here to help and support in any way we can in the next days and weeks."
He said that the group of classmates who had been on holiday with them are "absolutely traumatised" and are on their way home.
He said that the school is open, there is a book of condolences open and support is available to those who need it.
Several bouquets of flowers were placed at the Dublin school on Monday.
The Irish tricolour and the school flag were being flown at half mast outside the front door.
Mr Kelleher said: "We are heartbroken. We are a tight-knit community and these are two fantastic young men with their whole lives ahead of them.
"Bright, sporting, academic men, who had their whole lives ahead of them.
"There are hundreds and hundreds of families this morning plunged into deep, deep sadness because of what has occurred and again we are reeling with it.
"It's exactly the nightmare that every parent dreads when group holidays and big groups of children go away. You just don't want to get that call to say your child is missing.
"But two of our families have had that call and we are devastated for them, and our hearts are broken and our sympathy goes to them all."
The past president of St Michael's Union ,Tom McCormack, said it was the "darkest day" in the history of the Dublin school.
He said: "It was a devastating day, we've been heartened by the huge volume of messages of support from government ministers, councillors, senators, other schools.
"Our sister school, St Mary's, eight years ago had the Berkeley tragedy and we are now experiencing our darkest day."
The Tanaiste extended his condolences.
"I think we're all devastated at the loss of such young lives with such great potential, Andrew O'Donnell and Max Wall," Mr Martin RTE Radio One.
"And our deepest sympathies go to their parents, to their families and to the entire school community of St Michael's."
Mr Martin said he had spoken to the school principal on Monday morning.
He said: "They are devastated. Two outstanding young men with their lives ahead of them and our thoughts and our prayers are with the families and their friends.
"And obviously many of their friends are out there in Ios and it's a very, very difficult time for them now and we just ask them to look after each other over the next number of days and in the difficult time ahead."
