Hannah was less than 300ft from the summit

Hannah Shields, 37, from Kilrea tried to reach the summit of the mountain on Thursday.

But she became exhausted less than 300 ft from the summit and had to return to Camp 4 with the aid of a sherpa.

Hannah's father, Kevin, said he thought his daughter might want to make another attempt at a later date.

"Hannah always looks for near enough 100%," Mr Shields said.

"Looking at this through her eyes, she has just 97%. There is three per cent short," he said.

Liadain Slattery, spokesperson for the Irish Everest team, told BBC News Online that emotions were mixed, as two of the team's four climbers made it to the top and the other two did not.

Hannah was less than 300ft from the summit. It was within her reach. She got so close. Liadain Slattery Spokesperson

"Mick Murphy reached the summit at 0950 Nepalese time and Gerard McDonnell was on the summit at 1110 Nepalese time," she said.

"On the south summit at 28,710 ft, Hannah Shields became exhausted and had to go back to Camp 4 with the aid of a sherpa.

"Pat Falvey encountered problems also and had to go back."

Ms Slattery said she was "bitterly disappointed" for the two climbers who did not make it.

Blizzard conditions

Atrocious weather conditions had hampered the whole expedition, she said.

"Hannah was less than 300 ft from the summit. It was within her reach. She got so close."

She added that it was truly remarkable to get so far in blizzard conditions and to spend 36 hours at such altitudes with very little food.

Meanwhile, a team from Northern Ireland climbing Mount Everest is still hoping to reach the summit.

Northern hopes

Relatives and friends of the Northern Ireland summit team are waiting to hear news of their whereabouts.

Expedition leader Richard Dougan and his fellow climbers, David Sharp and Sherpa Ang Furi, had hoped to head for the pinnacle on Wednesday.

On Tuesday morning, using oxygen, they aimed to climb to Camp 3.

"The expedition last contacted www.nieverest.com on Monday when Richard Dougan and David Sharp arrived at Camp 2," expedition spokesman David Malone told BBC News Online on Thursday.

"We have not spoken to them directly since, though a Royal Navy team reported them safe and well at Camp 2 on Tuesday.

"It is our understanding that the team has communications problems which we hope will be resolved soon."

Mr Malone said losing communication was not unusual at such high altitudes.

"The higher up the mountain, the more difficult it gets.

"We will be a lot happier once we hear from them," he added.

The mountain's summit stands at 8,848 metres high, and beyond 7,600 metres climbers enter what is known as the "death zone" - so called because of the serious effects of oxygen deprivation on the body.

The lack of oxygen affects the lungs, confuses the mind, thickens the blood and can swell the brain.