Further tests will be carried out after the deaths of two soldiers during SAS selection training in the Brecon Beacons.
Edward John Maher and Lance Corporal Craig John Roberts collapsed on one of the hottest days of the year while climbing South Wales’s highest mountain.
A military colleague of theirs remains in a serious condition.
Witnesses on the day said they saw two soldiers “clearly in distress”, who pleaded with them for drinking water.
An inquest at Brecon Law Courts in Powys, mid Wales, gave the cause of death of the pair as “unascertained”.
Speaking at the hearing yesterday, Dyfed Powys Police Detective Inspector Ieuan Wyn Jones said that L/Cpl Roberts had been pronounced dead on the mountain at 5:15pm, while Mr Maher died at Prince Charles Hospital in Merthyr Tydfil almost three hours later.
“Post-mortems have been carried out and the causes of death are unascertained,” he added. “Further investigations are being carried out.”
The two soldiers were understood to be taking part in the aptitude training element of the course to become SAS reservists.
They were climbing Pen y Fan, the highest mountain in southern Britain, on 13 July.
It is known as the location for the “Fan Dance” where soldiers hoping to join the special forces march over the mountain carrying a heavy pack and a rifle, then do the route in reverse in a set time.
L/Cpl Roberts, 24, of Penrhyn Bay, had served with the Territorial Army for around five years and is understood to have served in Afghanistan and Iraq. The former teaching assistant lived in London and had been due to start a job in the office of the Education Secretary.
His father, Kelvin Roberts, said at the time of his death: “We are all devastated at the loss of our beloved Craig. This has left a massive hole in all our lives.
“We wholeheartedly supported Craig in his military endeavours and it gives us some comfort, though great sadness, that he died in the pursuit of his dream.”
Mr Maher was named as the second fatality by Ministry of Defence officials yesterday morning. His family issued a short statement saying: “At this time of great sadness, Edward’s family has asked that they be left alone to grieve in private.”
Following the deaths, investigations have been launched by both the police and the Health and Safety Executive (HSE).
Powys coroner Louise Hunt will also launch her own probe.
Before adjourning proceedings, she said a full inquest would examine all the circumstances leading up to the deaths and examine any “failings… if they are identified”.
Ms Hunt also said her investigation was not a “normal” inquest – any future verdict given must be independent and have the full involvement of both victims’ families.
“I would also like to place on record my deepest condolences to both families,” she added.
Proceedings were adjourned until 3 September, when they will resume at Aberdare Coroner’s Court.