TORONTO — Canada imposed mandatory self-isolation Wednesday for those returning to Canada under the Quarantine Act.

Deputy Prime Minister Chrystia Freeland initially said the system would begin at midnight Wednesday and require 14 days of isolation. But several hours later, government officials said the quarantine order had been in effect for more than 12 hours already.

“It will be a legal obligation for people entering Canada from outside Canada,” Freeland said. “Essential workers are excluded.”

Freeland said penalties would be announced later.

More than a million Canadians and permanent residents returned to Canada between March 14 to March 20, according to Canada Border Services.