TORONTO -- Detentions of Mexican nationals by Canadian border agents have surged dramatically this year to levels not seen in a decade, new figures obtained by The Canadian Press show.

According to Canada Border Services Agency, the total number of detentions from Jan. 1 into the first week of September hit 2,391 -- roughly six times the 411 in all of last year -- and equal to the previous five years combined.

"CBSA cannot speculate why the number has increased," spokesman Barre Campbell said in an email Thursday. "The agency's role is to apply Canadian law at the border."

The sharp increase has contributed to a rise in the rate of detentions of all foreign nationals this year. Figures show agents detained 1,032 people each month this year, compared to 877 a month last year and 993 in 2015.

Experts point to two main factors as the most likely cause of the upswing in Mexicans running afoul of border agents in Canada.

Last December, the Liberal government under Prime Minister Justin Trudeau lifted a visa requirement for Mexicans coming to this country, making it easier to do so. The result was an immediate jump in detentions.

Additionally, the crackdown on undocumented migrants under U.S. President Donald Trump and his threat to remove deportation protections from those foreigners who entered the States illegally as children -- the vast majority Mexicans -- may also have prompted many of those affected to look north to Canada.

Scott Bardsley, spokesman for Public Safety Minister Ralph Goodale, said on Thursday that Canada was working with Mexican officials to monitor migration trends and address any risks.

"Canadian officials have co-operated closely with Mexican counterparts to lay the ground work for the visa lift and ensure that appropriate safeguards are in place," Bardsley said in an email. "These efforts include measures to identify and deter irregular migration, including bolstering co-operation on travel-document integrity and traveller screening."

The last time the Mexican detention numbers were anywhere near current levels was in 2008, at 3,301, border agency numbers show. That year also saw the number of Mexicans seeking refugee status in Canada reach record levels.

In response to what they characterized as phoney refugee claims, the former government under then-Conservative prime minister Stephen Harper imposed an onerous visa requirement in 2009 that meant all would-be Mexican visitors had to provide numerous supporting documents.

"We are spending an enormous amount of money on bogus refugee claims," Harper said at the time. "This is a problem with Canadian refugee law, which encourages bogus claims."

Harper's visa decision resulted in an immediate plunge in detentions and asylum claims that lasted until 2015, with a slight uptick happening last year. However, the requirement angered the Mexican government and civil-rights groups in Canada among others, ultimately leading to Trudeau's reversal of that decision late last year.

Bardsley defended dropping the visa requirement as a boon to bilateral relations, trade, investment and tourism that he said will result in lasting economic benefits for Canada.

Recent Immigration and Refugee Board statistics also show a dramatic increase in asylum requests from Mexicans this year, although the vast majority of such applications are rejected as unfounded.

In 2016, for example, 242 Mexicans applied for refugee status. Almost three times as many -- 660 -- were recorded in the first seven months of this year alone. The board does not keep statistics of how many people came via the U.S. rather than from Mexico itself.

The law allows the border agents to detain foreign nationals or permanent residents on reasonable suspicion they pose a danger to the public, may go underground, or where identity is in doubt. The CBSA data relates to detentions not detainees and may include a person detained more than once.