Police take precautions in Mexico.

Auckland, April 27 NZPA - The Rangitoto College group at the centre of a swine flu alert originally thought they might be having a bad reaction to Mexican food.

Nine students and one teacher in the 25-strong party which arrived back in Auckland on Saturday morning after three weeks in Mexico have tested positive for influenza A.

Health officials believe it is likely they have swine flu, a strain of influenza A which has killed an estimated 81 people in Mexico.

The teacher stayed in North Shore Hospital overnight due to the symptoms of the disease, but she was expected to be discharged later today. A student was admitted on Saturday but has since been discharged.

All the infected students and their families have been quarantined at their homes.

The other students and teachers on the trip stayed home today as a precaution, while five students who played soccer with one of the returning students -- who had no symptoms -- were also sent home today as a precaution.

Three students from Northcote College who went on a separate trip and arrived back on a separate flight were also awaiting test results today.

Rangitoto College principal David Hodge said most of those believed to have the disease were responding well to doses of the anti-influenza drug, Tamiflu.

Mr Hodge has been constantly in touch with parents, health authorities and media since discovering the students may have contracted the disease on a three-week trip to Mexico.

"I became aware on Saturday that the kids had arrived home safely but aware that there had been illness on the trip," he told NZPA.

"Originally it was put down to Mexican food, which seemed like a good guess at the time."

The group were Spanish language students having three weeks in Mexico to give them language and cultural experience.

It was the first time the college had sent students there in the three years Mr Hodge had been principal. It had been in the planning for two years and required substantial fund raising.

The group arrived in Mexico City and did a loop around the central part of the country before spending their last three days back in Mexico City, where the outbreak had centred.

The students arrived back in New Zealand about 5am on Saturday and Mr Hodge was made aware of their illness soon after.

By noon public health authorities were in action, and 13 people with symptoms were tested.

Ten tested positive to influenza A, and were waiting for notice of test results from Melbourne to see if it was swine flu.

"We are not overly concerned about the state of health of any of the students," he said.

"We were a bit concerned about the teacher because she remained in hospital overnight, but she is being well looked after. "

With all those who went on the trip being kept at home on public health advice, along with those closely connected to them and those involved in the Saturday soccer match, it had been business as usual at the school today.

"We have had a fair share of concern from parents wanting information, which is absolutely understandable," he said.

"What we don't want is for fear to take over."

Northcote College students were not due to return to school until tomorrow due to a previously scheduled teacher-only day.

Principal Vicki Barrie said all of a 15-strong party which went to Mexico were contacted yesterday, and of them two students and a parent reported a mild sore throat. They had since been tested and were awaiting results.

All of those who went on the touring party had been asked to stay at home but families of those who had not reported any illness had been allowed by public health authorities to return to work, Ms Barrie told NZPA.

Unlike the Rangitoto College group, most of the Northcote group spent little time in Mexico City.

"They arrived in Mexico City and then travelled through Mexico and they left from Cancun," Ms Barrie said.

"They came home on a different flight than the Rangitoto College party and arrived home at a different time on Saturday morning."

There have been cases confirmed in five American states and suspected cases in Canada and France, as well as here, though it is only in Mexico that they have proved fatal.

NZPA AKL ajb sl gt