Neglect and delays in providing medical treatment contributed to the deaths of three British army reservists who collapsed during a grueling special forces selection march, a coroner ruled Tuesday.

Lance Cpls. Edward Maher and Craig Roberts and Cpl. James Dunsby all suffered from heatstroke on July 13, 2013, when the men were taking part in the military exercise in the Brecon Beacons national park in Wales.

The 16-mile (26-kilometer) hike took place on one of the year's hottest days.

Maher and Roberts were pronounced dead on the hills, while Dunsby died in a hospital two weeks later from multiple organ failure.

Coroner Louise Hunt said all three men died as a result of a "failure to properly organize and manage" the exercise.

Risk assessment before the march was inadequate, she said, adding that the three reservists "would have survived" if they received basic medical treatment in time.

Brigadier John Donnelly, the army's personnel director, apologized for the mistakes.

"It is necessary to train our soldiers to the high standards to meet the security challenges that we face both in this country and overseas and to do this requires our individuals to push themselves and take some risk," he said. "However, we must ensure those risks are carefully managed. In this case we did not do this and accept responsibility."