An experienced caver trapped in an underground cavern overnight on Saturday was simply too tall to climb through a narrow passage.
Lindsay Main, 62, was with his wife Alice Shanks and 16 other cavers in the Kahurangi National Park when he ran into trouble yesterday evening.
The group were on their way out of the Pillar Cave, near Salisbury Hut in the Tableland area of Mt Arthur at the time.
Bruce Mutton, a close friend of Mr Main and Ms Shanks and an experienced caver, said Mr Main had been unable to make it through a 15-metre long tight section, about 100m from the cave entrance.
Constable Malcolm York, search and rescue incident controller, said Ms Shanks returned to the underground cavern, about 60m in length, when it she realised her husband could not fit through the tight section.
"He was able to back-track out of the squeeze into the cavern.
"The other rescuers were able to pass through extra clothing through, equipment, food for them to be comfortable for the night,'' Mr York said.
Explosives were used today to widen the squeeze, he said.
"Very precise, very small charges were just able to break up the rock that was blocking the access. They [Mr Main and Ms Shanks] were given high protection gear and were able to move a good 60 metres away from the blast.
"It was just the sheer factor of him being taller, that compared to the other people, he couldn't bend his body into the gymnastic shape that was required,'' Mr York said.
The area of Pillar Cave the couple were in had a walking passage and the narrower passage which people needed to crawl through, Mr Mutton said.
"There were two right angle bends which made it quite difficult. It just so happened that going in it was easier than going out.''
Mr Main told TV3 the explosives made "a pretty good bang''.
"It shook the cave, even where we were probably 40 metres away.
''[We] did the cautious thing and stayed in the cave rather than pushing out and getting stuck in the squeeze,'' Ms Shanks said.
After the couple were rescued, they were checked over by medical staff and returned to to Mr Mutton's home in Nelson to warm up.
They were in good spirits, Mr Mutton said this evening.
"When they realised they were going to be trapped [overnight], they actually went back and did some more discovering.''
The couple, who live in Christchurch, were planning to return home tonight after their car was retrieved from Mt Arthur.
While Ms Shanks had a few bruised ribs from the trip, Mr Mutton was uninjured.
Pillar Cave is located on the western side of Mt Arthur.