Editor's note: After this story was published, CBC News obtained data from the CBSA showing that only three out of 135 asylum seekers in the month leading up to the assault on the border services officer mentioned in this story were deemed a danger to the public and detained. CBC News requested this data before the publication of the story but was initially told CBSA records could not be broken down to isolate that information. CBSA did provide some limited data five days after and CBC published a subsequent update.

Nearly half of the asylum seekers crossing the Manitoba border illegally in the last few weeks are being detained because of serious criminal records, suggesting the profile of would-be refugee claimants is changing, according to the union representing border patrol officers. It did not provide specific figures or context for that statement.

One of them assaulted a female Canadian Border Services Agency officer as he was being sent to lock-up at the Emerson, Man., port-of-entry last weekend, said Jean-Pierre Fortin, National President of the Customs and Immigration Union.

"She got hurt. I haven't seen the bruises but it's serious enough. But her life was not in danger," Fortin said, adding she has returned to work and does not want to be interviewed about her experience.

The RCMP confirms a 37-year-old man had illegally crossed the border at about 1 a.m. on Apr. 8. He was apprehended by RCMP officers before being searched, identified and screened. The man was taken to file his refugee claim at the CBSA office at Emerson.

As he was being sent to a cell, he threatened to harm CBSA officers, then physically assaulted one of them. He also damaged the fire sprinkler inside his cell.

Ahmed Aden Ali, from Minneapolis, was charged with two counts of Uttering Threats, Mischief Over $5,000 and Assault Peace Officer. He is being held in custody.

Border officers worried about safety

Jean-Pierre Fortin, National President of the Customs and Immigration Union, says nearly half of the asylum seekers crossing the border on foot at Emerson, Man., are being detained because of serious criminal records. (CBC)

The incident underlines safety concerns border officers have had for months, Fortin said.

"The officers in Emerson have noticed over the past few weeks, around 50 per cent of asylum seekers have [a] serious criminality record," he said.

Fortin did not provide any context for that statistic and at the time of publication, CBSA would not comment on it. However, the federal agency did confirm a CBSA officer was assaulted by a traveller resisting arrest.

"The officer sustained minor injury but did not require further medical attention. Our officers have the training and tools to respond to these situations," said a statement provided to CBC News.

Under Canada's immigration law, if someone has committed or been convicted of a crime, they may not be allowed into Canada because they're "criminally inadmissible." They're either detained or returned to their country of origin.

That includes crimes like:

theft.

assault.

manslaughter.

dangerous driving.

driving while under the influence of drugs or alcohol.

possession of or trafficking in drugs or controlled substances.

Someone convicted of a crime when they were under the age of 18 may still be able to enter Canada.

"I'm very happy to hear the officer is back at work and it wasn't a serious incident, but it's the beginning of what many residents in the area have feared, that the situation could turn into a situation of violence where their well-being is threatened," said Conservative MP Ted Falk, whose Provencher riding includes Emerson.

Nearly half of the asylum seekers crossing the Manitoba border illegally in the last few weeks are being detained because of serious criminal records, suggesting the profile of would-be refugee claimants is changing, according to the union representing border patrol officers. 1:49

Trudeau's tweet 'reckless'

"It's an issue that's very prominent in their minds and now with the MO [modus operandi] of individuals crossing the border seemingly changing, it's more of a real concern, and it's something the government needs to act quickly and decisively on."

Falk is calling on the federal Liberals to use Article 10 of the Safe Third Country Agreement to close the existing loophole allowing people who walk across the border to claim refugee status.

Canada is a signatory to the United Nations Refugee Convention, so those who sneak through the border at an unofficial point of entry can legally make a claim here, and they won't be prosecuted for the illegal entry.

Hundreds of asylum seekers have crossed the international border so far this year at Emerson, Man. The union representing border patrol officers says half of them in the last month have been detained for serious criminal records. (Karen Pauls, CBC News) "The careless and reckless response from our PM when he tweets out, 'Welcome to Canada, no matter who you are and where you come from, there's a place for you in Canada,' that message is resonating with people who are opportunistic, and in this case, it looks as though we're seeing people who are actually fleeing the law," Falk said.

In Question Period on Thursday, Conservative MPs asked Public Safety Minister Ralph Goodale why RCMP and CBSA officials were only providing information on illegal border crossers once a month.

"Individuals on the ground are saying this gag order came from Ottawa," Falk said.

"The public deserves to know how many people are illegally crossing the border into Canada," added Conservative MP Michelle Rempel. "Covering up these numbers will not make problems go away for the Liberals. Without these numbers, local officials cannot plan to cope with the situation and the government cannot be held to account by us."

Goodale said information for March should be available "in the next number of days."

"We are collecting all of the data from all of the departments and agencies of the Government of Canada that are relevant to the situation, and making sure that they are presented publicly, providing more information about the situation than has ever been provided before," he replied.

Meanwhile, Fortin said the union wants Ottawa to put more officers on the border in Manitoba and Quebec — not just shift them from existing detachments.

Union wants more staff, powers

"Our officers are under a tremendous amount of pressure to speed up the process with regards [to] the procedures surrounding the demands of asylum seekers," he said.

"Normally, to do one file of that level, you're talking about at least eight hours of work, but we're being pressed by the employer right now to speed up the process. This is a concern because we want to make sure Canadians remain safe and that officers have the time to proceed [with] each case individually and to scrutinize all of these demands."

The union also wants an expanded mandate so CBSA officers can do surveillance in between Canada's 117 ports-of-entry. Right now, that is RCMP jurisdiction.

"When we're at the point where our officers are getting assaulted like this case that got reported last weekend, it tells a level of danger or potential danger, especially when you're talking about people crossing at the border illegally," Fortin said.

"Obviously the government will need to take a very clear stance on this matter right now."