A Canadian citizen detained in China earlier in December has been released and returned to Canada, according to the government in Ottawa.

Canada’s national broadcaster, the CBC, identified the citizen as Sarah McIver, a teacher. China’s foreign ministry said earlier this month that McIver had been undergoing “administrative punishment” for working illegally.

McIver was the third Canadian to be detained by China following the 1 December arrest in Vancouver of Meng Wanzhou, chief financial officer of the Chinese telecommunications company Huawei. A Canadian official said there was no reason to believe the woman’s detention was linked to the prior arrests.

The Canadian foreign minister Chrystia Freeland did not mention the woman in calling for the release of the other two Canadians last week.

China arrested two men – former diplomat Michael Kovrig, employed by thinktank International Crisis Group, and Michael Spavor, a consultant on North Korea – on 10 December. They were detained on suspicion of “harm to national security”, a phrase often used by Beijing when alleging espionage. But it was seen as retaliation following the arrest of Meng Wanzhou.

Ottawa has repeatedly said Meng’s arrest was not political but rather part of a judicial process in keeping with an extradition treaty with Washington.

Further testing tense relations, another Canadian, Robert Lloyd Schellenberg, is due to appear before a court in north-eastern China on Saturday on drugs charges. A Chinese government news portal, runsky.com, identified Schellenberg as Canadian and said he was accused of smuggling an “enormous amount” of drugs.