Foreign patients receiving medical treatment in the Bay of Plenty - some skipping the country without paying their bill - owe close to $280,000.
The figure is more than four times higher than the previous year with some of the debt likely to be written off.
Foreign patients treated locally owed Bay health authorities $277,346 in unpaid bills from a total of $793,367 racked up in medical expenses in the year to June 30, according to figures released to the Bay of Plenty Times under the Official Information Act.
This figure had ballooned from $65,845 owed at the same time the previous year, despite the board's efforts to crack down on unpaid medical bills.
Conditions that landed foreign patients in Bay of Plenty hospitals included premature birth, gastroenteritis, post alcohol seizures, hernias and heart failure.
A number were also admitted for abdominal pain and rashes.
Bay of Plenty District Health Board manager of governance and quality Gail Bingham said about 200 foreign patients failed to pay their bills in the year to June 30 - six of which had since been written off at a value of close to $3100.
"Our system does not track bad debts by location however we estimate approximately 10 of these people are no longer resident in New Zealand," she said.
"All debts are held for 12 months before being written off and are only written off if there is no payment plan in place."
The sharp increase from the previous year could likely be explained by one particularly expensive admission.
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"If you get an ineligible patient who is admitted to an intensive care unit, their bill would be quite high," she said.
However, the amount outstanding was "quite small" compared to the total volume of health care the board provided, she said.
The number of foreign patients being treated was going up nationwide, she said.
"We're not likely to be any different."
A crackdown a few years ago seemed to have saved the Bay of Plenty DHB thousands of dollars. In September 2011, the DHB introduced rules requiring all patients seeking non-urgent care to prove they were New Zealand citizens and pre-pay for elective operations and out-patient care. The amount owing then dropped from $177,923 in the 2011 financial year to $65,845 the following year.
However, that figure had more than quadrupled in the year to June 30, 2013.
New Zealand has a reciprocal free health care arrangement with residents from Australia and the UK, plus citizens of Tokelau, Niue and the Cook Islands.
Foreigners who suffer injuries as a result of accidents are covered by ACC.
Nationally, the amount owed by foreigners in unpaid medical bills was not centrally held, a Ministry of Health spokesman said.