CALGARY -- As the number of COVID-19 cases in Alberta rose to 56, the province's top doctor said several new infections came from a single gathering in the Calgary zone.

Dr. Deena Hinshaw said there were "several concerning elements" to the 17 new coronavirus cases that emerged over the weekend.

For the first time in Alberta, cases were spread through community transmission, where people acquired the virus without having travelled abroad recently.

Seven of the new cases came from a single gathering in the Calgary health zone, Hinshaw said, underlining the need for people who have symptoms to stay at home.

"This underlines the fact that gatherings can accelerate the spread of the virus," she said.

Hinshaw, Premier Jason Kenney and Education Minister Adriana Lagrange also announced that classes at all Alberta-area schools and post-secondary institutions would be cancelled, and daycares would be closed as well.

While schools will be closed to students, teachers and other school staff will be expected to continue their regular day-to-day operations and administrative work.

Diploma exams for Grade 12 students will still go ahead.