Statistics Canada is blaming a computer error for results that indicated a surprising increase in the number of English-speaking people in Quebec.
The agency said roughly 61,000 people were misclassified when the results of the 2016 census were compiled.
"We are working diligently to correct the information and publish updated findings next week," Statistics Canada said in a statement released Friday afternoon.
"We are also taking steps to further strengthen our quality control procedures."
English-language groups in Quebec alerted Statistics Canada to possible discrepancies earlier this week.
They'd been puzzled by results that showed large spikes in the number of native English-language speakers in some parts of the province.
For instance, in Rivière-du-Loup, 135 people reported having English as a mother tongue in 2011. In 2016, that number was 240.
Some small communities that previously had no anglophones suddenly found themselves with many, according to the data. The village of Sainte-Thècle northeast of Shawinigan, for instance, changed from zero anglophones to 50. It has a population of 2,400.
Most of the errors are on the local level, said Marc Hamel, director of the census at Statistics Canada.
"This probably doesn't impact the results for Montreal," Hamel told CBC News. "In small communities around Quebec, where the proportion of the population speaking English is small, you should see a difference in what you would expect."
Anglophone groups spotted the anomalies
The Quebec Community Groups Network, a group that represents Quebec English-speaking communities, partnered with historian and demographer Jack Jedwab, who compared the number of anglophones to the English school enrolment rates and Quebec immigration rates.
"The increases, I would say, are impossible," said Jedwab. "I don't know where the people are coming from."
Jedwab was pleased with the speed at which Statistics Canada acknowledged the errors. He hopes that the adjusted numbers will lead to a more "reasonable discussion" around language in Quebec.
When the figures first came out, there were concerns about a decline in French as a mother tongue in Quebec.
"Hopefully it will make people rethink conclusions they drew around the situation of the French language in Quebec outside Montreal and rethink the types of services delivered to anglophones outside Montreal," Jedwab said. "It will remind us that this is a population that is still vulnerable."