Over a recent one-month stretch, three people intercepted by RCMP while crossing into Canada on foot near Emerson, Man., were detained because they were found to be a danger to the public, Canada Border Services Agency officials say.

Between March 20 and April 16, 135 asylum seekers were found illegally crossing the border near the small Manitoba town.

Details released Wednesday show the number of asylum seekers crossing the border into the province is climbing.

In March, 170 people were intercepted crossing into Manitoba — up from 19 in January and 142 in February, according Citizenship and Immigration Canada.

The union representing border patrol officers raised concerns about public safety last week, saying nearly half of the asylum seekers entering near Emerson in the last few weeks have some criminality in their backgrounds.

Data provided by the Canada Border Services Agency doesn't include numbers about asylum seekers with criminal backgrounds who were not detained. The CBSA does not keep statistics on asylum seekers with records who have not been detained.

Jean-Pierre Fortin, national president of the Customs and Immigration Union, said border officers have been under increased scrutiny in recent months and will only detain an asylum seeker "as a last resort."

One of the recent detainees allegedly assaulted a female officer on April 8.

Ahmed Aden Ali, who came to Canada via Minneapolis, was charged with two counts of uttering threats, mischief over $5,000 and assaulting a police officer.

People can only be detained at the border for three reasons: They're a danger to the public, they're unlikely to appear for a removal hearing or their identity can't be determined.

Border services officials said they didn't know whether the three people who were recently detained are still in custody. They may have been released by the Immigration Refugee Board on a promise to appear before the board for a removal hearing at a later date.

Someone can be deemed "criminally inadmissible" to apply for refugee status in Canada but may still be released into the country on a promise to appear at a future removal hearing.