A 10-year-old Christchurch boy watched 12 of his classmates swallow an unknown white pill around the back of the bike sheds before school this morning.

Cody Lecomte later saw his Northcote School friends crying as they were loaded into ambulances and taken to Christchurch Hospital.

Cody said he was offered one of the oval-shaped pills but decided to turn it down.

"I said no because I didn't really want to take any and they could have been bad and they could have killed you. I was scared that I could get hurt from it," Cody said.

A 6-year-old pupil had found the pink container of pills on the ground as she walked to school and given it to her older sister who had handed the pills out among friends behind the bike sheds, he said.

"They were white, long and oval in a pink slidey case that had writing on it."

Some of the pupils swallowed the pills and a few spat them out, he said.

His classmates were "walking around and just acting fine" after they had taken them.

One of the pupils who was involved decided to tell a teacher about the pills before the 9am bell rang.

"My teacher came in and asked us: 'Did any of you guys take any pills'," Cody said.

The 12 pupils who had swallowed a pill were quickly identified and collected from a number of different classrooms, he said.

The children were taken to the school office and St John ambulance was called.

Cody said it was "scary" when three ambulances arrived at the school to treat his friends.

"They were all crying in the back of the ambulances because they were scared of getting hurt from the pills."

After the ambulances left, Cody said a teacher came into his classroom to "talk about never taking pills like that".

Cody's father, Mike Hurst, said he was "proud" his son had declined to take the pill.

"He's listened to what I have taught him," he said.

PUPILS DISCHARGED FROM HOSPITAL

The 12 pupils sent to hospital after taking mystery pills have been discharged, after testing revealed the tablets were a herbal remedy.

A Canterbury District Health Board spokeswoman said testing of the pills revealed they were "consistent with that of a herbal remedy", with no adverse or long-term effects likely.

The herbal pill contained a geranium extract, said the spokeswoman.

The spokesman said the children were being discharged with information explaining the dangers of taking unidentified tablets.

Parents were also being told to contact emergency services if their children had any problems, although that was not expected to be an issue.

St John said the pupils were taken to hospital at 10.10am after paramedics were alerted.

"None are in a serious condition, however some are complaining of stomach pains, so all of them need to be assessed and receive further treatment at hospital," said spokesman Ian Henderson.

Northcote School principal Neil Baker said while the children, aged seven and eight, seemed fine, paramedics had decided to take them to hospital for observation in case any problems developed.

Baker said the school would also speak to all their children about the incident so there was no repeat in the future.

"The warning signs should have gone off, the fact that it was an unknown container, and when we talk to them I think they'll know that they shouldn't have done it."

- © Fairfax NZ News