TORONTO -- Up to 30 people may have been exposed to a used needle during blood sugar tests conducted at a community event in Toronto last month, the city's public health authority said Monday as it urged those affected to see a doctor as a precaution.

Needles were "not consistently changed between clients" during the free tests at the March 25 health fair organized by the Vision Infinite Foundation, a Bangladeshi-Canadian community group, said Dr. Herveen Sachdeva, an associate medical officer with Toronto Public Health.

There is a very low chance of blood-borne viruses, such as hepatitis B and C and HIV, being transmitted by re-using a lancet -- a fine needle typically used to prick the skin and take small amounts of blood -- but Toronto Public Health has called and written to everyone who had their glucose levels checked at the fair, recommending they get blood tests as a precaution, Sachdeva said.

"Toronto Public Health will receive the results of those who present for follow up with this testing ... and this will help us understand whether any illness may have been associated with this event although the risk is very low," she added.

A woman who attended the fair held at a community centre in Toronto's east end told organizers during the event that she had seen testers re-use a lancet, Vision Infinite director Shahid Khandker said.

Organizers immediately shut down the testing station, which was run by pharmacy staff from a nearby Shoppers Drug Mart, and called paramedics who in turn notified Toronto Public Health, he added.

"For the future, whether the pharmacy is given the opportunity (to participate again) or not, there are going to be more precautionary measures for sure," Khandker said of including blood tests at other Vision Infinite events.

Pharmacist Ahmad Abdullah, who said a member of his staff was administering blood sugar tests at the fair when the complaint was made, said it is "extremely disturbing" to know a lancet may have been re-used.

"This kind of thing shouldn't happen but unfortunately, when there are lots of people there, maybe staff just missed it by chance," he added.

Abdullah said he provided Toronto Public Health with a list of everyone who had their blood tested, so authorities could contact them.

Any pharmacy staff member can perform blood tests as long as they have been trained and are supervised by a pharmacist, Abdullah said.

Sachdeva said Toronto Public Health is "looking into what training and qualifications are required" to perform blood sugar tests.

"We will continue to follow up accordingly with the staff from the health fair," she said. "Toronto Public Health staff continue to investigate the matter and the event organizers have been co-operative."