A couple who operate an Oshawa convenience store have been arrested on drug charges after first being investigated on allegations of selling cigarettes to underage children.

"That was a 'happen-upon,'" Sgt. Nancy Van Rooy told ctvtoronto.ca on Friday.

Students told a school official that the store was allegedly selling individual cigarettes for 50 cents each to children between the ages of 10 and 12, she said.

As a result, the official told a Durham Police school liaison officer, who contacted a tobacco investigations unit with the provincial revenue ministry.

On Thursday, members of that unit went to the story to do a compliance check on the store. "When they arrived ... they saw this bucket of candy that was packaged with individual bags of drugs," Van Rooy said.

Durham police officers went to the store. They found the bucket contained marijuana as well as Oxycodon and Percocet tablets, along with Dilaudod pills. Those last three are heavy-duty, opiate-based painkillers.

The husband and wife "had their own children there -- at two in the afternoon on a school day -- with this sort of drugs around and whatever else," Van Rooy said.

As a result, the Children's Aid Society has been contacted. The children are aged 5, 8 and 11.

A 42-year-old male and 39-year-old female are each facing a charge of possessing marijuana and three each of possession of controlled drugs.

Van Rooy said there is no allegation the individuals were selling drugs to minors.

She said they will not be named to protect the identity of their children.

Durham police say the investigation is ongoing. They ask people with information to contact 17 Division at 1-888-579-1520 ext. 5100 or contact Crime Stoppers if they want to remain anonymous.

Back in late February, Durham police unveiled the results of an undercover drug operation that began with complaints that marijuana was being sold out of an Oshawa fishing shop.

Van Rooy said drug dealing out of otherwise legitimate businesses appears to "fortunately" be a rare occurrence. "That or we haven't been notified as often as we need to be that this sort of thing is going on," she said.

"Let's hope it's a very infrequent situation and we won't have repeats."