A former Pike River Coal miner believes methane gas at the mine made him ill.

His symptoms included dizziness, high temperature and disorientation," the man, who asked not to be identified, told the The News of Westport.

"I got real sweaty and I didn't know what I was doing."

Methane gas is suspected of causing the massive explosion at the mine last Friday. Nothing has been heard from 29 miners and contractors since then.

The ex-miner said the symptoms, which he had never experienced before, began about a month after he had started work at the mine.

He had had "blood tests, x-rays, everything", which had proved inconclusive.

"The doctor is still making further inquiries in Christchurch."

After three weeks sick leave he decided to quit the mine. He now has another job and says his health has improved, he said.

One of his mates at Pike had had similar symptoms and was still on sick leave after about six weeks. Other miners had also been sick, but he was unsure of their symptoms.

Methane gas depletes the body of oxygen. Symptoms of exposure include dizziness, blurred vision, lack of co-ordination, difficulty thinking, headaches and heart palpitations.

The miner said Pike mine had been dealing properly with its methane gas problems, but the mine needed more monitoring. Each team of miners had a set of gas monitoring gear between them.

"The deputies are walking around and testing, but we never got told of what the levels were...that gas, you can't smell it."

He believes Pike had a future as an opencast rather than an underground mine.

"They can still use the system they've got to get the coal off, even if they take the top off. And that will let the gas out."

Engineering, Printing and Manufacturing Union (EPMU) national secretary Andrew Little said he had never heard of any Pike mineworker becoming sick from the gas.

"I was told there was a pretty active health and safety committee there. They were meeting on a regular basis," he said.

He would not be averse to the mine becoming open cast, but said that would have to be a political decision. Pike had gone underground to avoid harming conservation land.

Mr Little said EPMU members in Grey were "completely shattered" by the mine disaster. "That's their colleagues who are underground and it could have been them. It could have happened at any time. Long serving miners who have been at that mine for a long time are just absolutely devastated."

Not knowing what had happened to the 29 trapped men was the worst thing, he said.

"Eventually, the hope starts fading and that's the real tragedy of it."

Pike River Coal had done an excellent job responding to the disaster, he said.