Canadian nurses working at Michigan hospitals were shocked last week when border security officers stopped them from entering the U.S. and advised them there were issues with their working visas.

Staff at Detroit's Henry Ford Hospital heard reports of nurses unable to renew their working visas. Last week, a new Canadian hire at Henry Ford tried to go to work, but was turned away at the Windsor-Detroit border.

She was incorrectly told advanced practice nurses and nurse anesthetists no longer qualify for the working visas because of policy changes under U.S. President Donald Trump.

"We really question the motives," said immigration lawyer Marc Topoleski, whose firm is retained by the hospital. "All of the immigration executive orders and all the things being rolled out have been focused on national security first, and this is clearly not an issue of national security whatsoever."

'Livelihoods are at stake'

Only advanced practice nurses and nurse anesthetists are being rejected. All Canadian nurses working in the U.S. have non-immigrant NAFTA professional (TN) visas.

An estimated 30,000 to 40,000 Canadians work in the U.S with TN visas, which allow experts in certain fields — like economics and science — a fast track, provided they have a job offer.

Henry Ford Hospital alone has hundreds of Canadians on staff, with about 25 advanced practice nurses or nurse anesthetists with TN visas.

"Some of these things are surprising," said Patrick Irwin, vice-president human resources at Henry Ford Hospital. "We have always been able to qualify these nurses under the TN category."

CBC News contacted U.S. Customs and Border Protection for an interview, but has yet to get a response.

Hospital officials said they're doing everything they can to resolve this issue.

"Their livelihood is at stake," Topoleski said. "They don't know why this is happening, they don't understand why it's happening. All they've been doing is just coming here and helping Americans get better by providing patient care."

Michigan's Council of Nurse Practitioners is trying to make their members aware of possible problems at the border, according to executive director Olivia McLaughlin.

"It's obviously concerning for a number of reasons," she said. "This seems like a recent opinion that is affecting the renewals."

'It just makes absolutely no sense'

The nurses have been advised they need to apply for H1B visa status, which is a separate category under NAFTA for more specialized employment. But those applications can cost between $3,000 and $4,000 depending on the applicant, according to Topoleski.

Other policy changes recently announced by the U.S. Citizenship and Immigration Services will suspend a fast-track program for processing H1B applications as of April 3.

Standard application processes for work visas could then take six months or more, said Topoleski, who worries long wait times could hurt hospitals that are in desperate need of specialty nurses.

"These specialty nurses are hard to find. There's more positions than there are people available," Topoleski said. "They're coming here to help our patients. I just don't understand what the policy goal is by doing something like this, it just makes absolutely no sense."