A Vancouver law firm is raising concerns about the reliability of a federally approved roadside drug screening device, saying the machine returned false positives for people who had not recently used drugs.

"The issue is, does it fit in the Canadian legal context," said Paul Doroshenko of Acumen Law. "And I'm more and more thinking that it doesn't."

Acumen Law bought a Drager DrugTest 5000 to put the machine through its paces and see if it returned accurate results.

The firm claims the machine returned a positive result during testing for opiates for a person who had just eaten a poppy seed muffin.

Doroshenko himself drank a tea, which he chose not to name but says is widely available in Vancouver, and shortly afterwards tested positive for cocaine when his saliva was run through the machine.

A third person consumed CBD, a cannabis extract that doesn’t produce a high or cause impairment, and tested positive for THC.

"How much testing has been conducted?" asked Doroshenko. "We've done some tests that we can do, and we will continue to, but ultimately it probably raised more questions for us than answers."

Asked about the machine's reliability, the province’s top cop deferred to the federal government.

"They said they have gone through comprehensive testing, that it's a technology that's used in many other jurisdictions," said Public Safety Minister and Solicitor General Mike Farnworth. "But I've said all along, whenever something like that is introduced I fully expect it is going to be challenged."

In an email, the Department of Justice tells CTV News the machine underwent rigorous testing by the Drugs and Driving Committee of the Canadian Society of Forensic Science before its approval.

The federal government says it has confidence in the recommendation by that organization and has no plans to perform further testing or evaluation.

The email also stated the approved Canadian version of the device only tests for cocaine and cannabis, and not opiates like the model used by Acumen Law.

No RCMP detachments in BC are currently using the Drager DrugTest 5000, and neither is the Vancouver Police Department, which says it relies on the standardized field sobriety test to detect drivers impaired by drugs.

Doroshenko says if any of his clients are charged based on results from the machine, he looks forward to challenging the test in court.