The number of missing or murdered indigenous women in Canada since 1980 may be as high as 4,000 - far more than previous estimates of 1,200, the federal government has said.
The minister for the status of women said there were no accurate figures because of a lack of hard data.
But Patty Hajdu said research from the Native Women's Association of Canada (NWAC) put it at more than 4,000.
A national inquiry is due to begin shortly.
Ms Hajdu and Indigenous Affairs Minister Carolyn Bennett have been speaking to survivors and relatives across Canada.
The inquiry was a key election pledge by Prime Minister Justin Trudeau during the campaign last year.
The often cited 1,200 figure came from a 2014 Royal Canadian Mounted Police report on the missing women, related to the period between 1980 and 2012.
"During those discussions, the ministers have heard from participants that they believe the number of missing and murdered indigenous women and girls is higher than 1,200," Ms Bennett said.
In December 2015, Canadian authorities charged a man in the death of one indigenous girl whose murder caused a national outcry.
Raymond Cormier, 53, was charged with second-degree murder in the death of Tina Fontaine, 15, who was found dead in 2014 in Canada's Red River.
A BBC investigation in April revealed that dozens of aboriginal women disappear each year, with many later found dead in the river.
Mr Trudeau has promised an inquiry into missing and murdered indigenous women in an appeal to First Nations chiefs.
The public inquiry would be a "top priority" of his newly-elected Liberal government, he said.
Mr Trudeau also pledged increased funding for programming and a review of laws on indigenous peoples.
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Justice Minister Jody-Wilson Raybould, Ms Hajdu and Ms Bennett conducted interviews with nearly 2,000 people to start forming the government inquiry, involving survivors, families and loved ones of survivors.
The ministers wanted to "examine the causes of violence against Indigenous women and girls and leads to recommendations for concrete actions to prevent future violence", said Ms Bennett.
"Regardless of the number, the level of indigenous women and girls who have gone missing or were murdered is an ongoing national tragedy that our government is committed to addressing immediately."