MINOT (AP) - The Minot landfill has temporarily stopped taking waste from Trinity Hospital, after the discovery of unauthorized medical waste.

Trinity spokesman Randy Schwan said officials are working to determine how it happened and to increase oversight of hospital waste.

"We are working with city officials to resolve it and identify the sources of regulated medical waste they found at the landfill," he said.

Landfill staff earlier this month discovered trash bags from Trinity containing regulated infectious waste mixed with other garbage, Minot public works director Alan Walter said. The incidents involved both improperly bagged waste and waste that should not have been sent to the landfill, which is not licensed for infectious waste, he said.

The North Dakota Health Department has written a letter of warning to the hospital. Environmental scientist Christine Roob said the department will take no further action if it is satisfied with Trinity's response.

Walter said the city expects to resume accepting waste from Trinity on Thursday, once the hospital completes training for employees on proper waste handling.

The landfill stopped accepting hospital waste on Friday. Trinity does not expect a garbage backup because its regular pickup is once every five to seven days, Schwan said.