Residents of the oil-rich province of Alberta vote Monday in a referendum on whether to stay in Canada or start a process toward a legally binding secession vote.

Recent polls show about 70% of residents favor remaining part of Canada, while roughly 20% favor secession and the remainder are undecided.

Alberta Premier Danielle Smith, Canadian Prime Minister Justin Trudeau and both of the country's major political parties have repeatedly opposed secession. Support for the independence movement has also come from former U.S. President Donald Trump.

Alberta, a province of about 5 million people, has about 3.1 million eligible voters, according to Elections Alberta, the province's election authority.

Polls open at 9 a.m. (3 p.m. GMT) and close at 6 p.m., though advance postal and in-person voting has already taken place.

Voters will decide 10 questions. The secession question will be counted first. Results could be available as early as Tuesday, according to election officials.

Calgary, with about 1.68 million residents, is Alberta's largest city, followed by the capital, Edmonton, with about 1.28 million. Its national parks in the Rocky Mountains attract tourists worldwide.

Alberta has some of Canada's most conservative voters. A movement advocating independence on cultural and economic grounds has existed for years.

Some oil industry representatives feel environmental regulations restrict them, while many protesters who opposed coronavirus restrictions and vaccine mandates later joined the independence movement.

Although the movement has long represented a minority of Albertans, it persuaded Smith, the province's conservative premier, to call the referendum. Smith herself has consistently advocated remaining part of Canada.