Canada is sending three helicopters to the Philippines to help disaster relief efforts in the aftermath of Typhoon Haiyan, where 51 Canadians remain unaccounted for.

Two of the three Griffon helicopters will be sent out by cargo plane on Sunday, with the third likely departing Tuesday. Canada has said cargo planes are now expected to depart every two days, for the foreseeable future, with people, equipment and supplies bound for the Philippine island of Panay, where the Canadian aid response is focused. The helicopters join just over 200 Canadian soldiers that have been dispatched as part of Canada's Disaster Assistance Response Team, or DART.

The dispatch of helicopters comes as Canadian officials continue to work to contact citizens believed, by family and friends, to have been in the region when the typhoon struck. After the storm, the federal government heard from friends and families of 187 Canadians in the region. So far, 136 have been contacted, all of them unharmed. The remaining 51 remain unaccounted for.

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A Foreign Affairs spokesman said in a statement the department is working around the clock to contact the remaining 51, a task it expects will become easier once communication channels are restored in the aftermath of the storm. "We urge Canadians who are in the affected areas to contact and reassure their loved ones, even if they have not been affected by this event," the department's statement said.

No Canadians have been confirmed to have been injured or killed by the typhoon.

The helicopter air crews will be sent from CFB Edmonton, while the helicopters themselves are coming from Quebec and Ontario. The Griffon is a multipurpose helicopter that can deliver aid or DART crews into remote areas, or rescue people stranded by last weekend's storm. It can also conduct search-and-rescue missions, if needed. The helicopters give DART "additional means to reach and help those who desperately need our assistance," Defence Minister Rob Nicholson said in a written statement on Saturday.

The flight time to the Philippines for Canada's C-17 cargo planes is roughly a day and a half, so the helicopters likely won't arrive until late Monday, or Tuesday morning in the Philippines, 10 days after the storm struck. Canada has elected not to deploy any ships to the Philippines - it had sent two to Haiti after the 2010 earthquake - because the travel time would be too long to make the ships worthwhile.

The Griffons have been used internationally before, including in Jamaica in 2011, Haiti in 2010 and 2004, and throughout much of Canada's war in Afghanistan. They've also been used after disasters within Canada, including Eastern Canada's ice storm in 1998 and after flooding in Manitoba in 1997 and 2011.

Canada dispatched DART on Tuesday. It's unclear how long the soldiers will stay or what the mission will cost, though the team typically plans for a 40 day departure. "Right now, our priority is providing help to the Philippines. I think Canadians would agree that this is money well spent," Julie Di Mambro, a spokeswoman for Mr. Nicholson, said in an e-mail Saturday when asked about the mission cost.

Canada has pledged $5-million in relief aid to the Philippines, and will also match private donations made until Dec. 9.

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Philippine authorities asked Canada to head to Panay, though the damage there is minimal compared to Tacloban and other hard-hit regions. Canadian officials say the risk in these areas is largely the spread of disease, as evacuees are huddled together in areas with poor water quality and insufficient sanitation facilities.