A misunderstanding involving two Toronto hospitals is being blamed for some 700 confirmed GTA cases of COVID-19 that were not flagged to public health officials.

The positive tests were completed as far back as April but the health units involved were only informed about them in the past few days.

The bulk of the cases involve people living in Toronto, York Region and Peel Region.

The oversight means thousands of contacts of confirmed cases were not traced by public health workers, potentially contributing to wider spread of the coronavirus in recent weeks.

The tests were conducted by the William Osler Health System, which has hospital sites in Etobicoke and Brampton as well as a drive-through COVID-19 assessment centre.

The test samples went to Mount Sinai Hospital for processing and each hospital thought the other was responsible for the reporting.