A Minnesota senior was jailed by Canadian border guards at a Manitoba port of entry after a jar containing some motor oil was mistaken for heroin.

Janet Goodin, 66, a retired girl scout registrar and grandmother of 12, was on her way to Sprague, Man., from her home in Warroad, Minn., in April when she was questioned at the border, she told CBC News on Tuesday.

Janet Goodin was mistakenly accused of smuggling heroin into Canada when a jar of used motor oil tested a false positive for the drug. (CBC)

The guards, with the Canada Border Services Agency, then searched her minivan and found a canning jar containing a dark liquid.

A cursory test of the liquid convinced guards it was the illicit drug and Goodin, who was heading to Canada to play bingo and visit her daughters, instead found herself heading to jail.

She was handcuffed, arrested and charged with possession of a drug for the purpose of trafficking as well as importing a controlled substance.

"I couldn't even think, I was so astounded," Goodin said.

'The inmates were all very good to me. I wasn't afraid of them at all'—Janet Goodin

"I said, 'That's not even possible.' I said, 'I'm sure it's oil that was put in there that was left over or something.' And they said, 'No, it tests positive for traces of something.'"

She had no money for bail and spent 12 days locked up at the Winnipeg Remand Centre before further testing proved the liquid was not heroin after all.

"The inmates were all very good to me. I wasn't afraid of them at all," Goodin said.

"But being locked up and [to] not know if I would ever get out in my lifetime, it was just … it was so scary."

Goodin hasn't been given an explanation from Canadian officials about what happened, or been offered an apology. She would like both and has retained a lawyer to look into filing a lawsuit.

More lab testing should have been performed prior to charging and detaining Goodin, said Scott Newman, a lawyer who represented her at the time of her incarceration.

"They should have waited until further lab tests had indicated whether or not there was in fact heroin in the motor oil," Newman said. "The other difficulty is a test like that only indicates the presence or absence of something; it doesn't say how much."

Public Safety Minister Vic Toews said he would be receiving a report from the Canada Border Services Agency on the case, but would not comment on "operational matters."

"Obviously, in that particular case, the officers had some indication that there was an illicit product and that individual had to be detained," he said.

But the minister said he would not comment on the merits of the arrest until after he has viewed the border agency's report.

Janet Goodin of Warroad, Minn., was on her way to play bingo and visit her daughters in Sprague, Man., when she was arrested.