Authorities in Ethiopia have detained 13 Canadian healthcare workers and volunteers, alleging the group were improperly practising medicine in the country.

Canadian Humanitarian, a non-profit organisation based in the province of Alberta, confirmed the detentions but denied allegations it had distributed expired medication or was offering medical services without prior approval.

“The care they provide in Ethiopia is the same care they would provide here in Canada. We are vigorously defending the actions and decisions of our team knowing that every decision was made by highly trained and certified Canadian medical professionals and that their mission on this trip was to provide essential medical care to the citizens of Ethiopia who need it most,” Canadian Humanitarian said in a statement on its website.

Global Affairs Canada has confirmed it is aware of the detentions and that consular officials have been in contact with the Ethiopian government.

The group were travelling in the mountainous northern city of Gondar when they were detained on Friday. In addition to 10 volunteers, three Canadian staff members and two local employees were taken into custody.

“Just like all of our trips, our team and organisation followed all necessary steps and protocols to ensure our group had all permits needed to provide medical support and care while in Ethiopia,” the charity said. It added it had enjoyed “longstanding, positive, and collaborative relationships” in the country for more than 15 years.

Rob Oliphant, the parliamentary secretary to Canada’s foreign minister, told the Globe and Mail newspaper that Ethiopia had so far been “cooperative and helpful” by permitting consular access to the detainees, who have been remanded for two weeks. But he cautioned that officials in the country “can’t interfere or step in” to impede a police investigation.

Oliphant has confirmed that the Canadian ambassador to Ethiopia, Antoine Chevrier, will be present on Tuesday when the Canadians can appeal against their detention.

Canadian Humanitarian said it would not comment further on the issue nor would it release the names of those in custody.