Supporters of a growing movement to blockade the Muskrat Falls hydro project in Labrador over methylmercury concerns say it's a test of Justin Trudeau's bid to reconcile with aboriginal people.

"Step up," Jim Learning, an Inuit resident and longtime critic of the project, urged the prime minister Thursday.

"Back us up, because there are three aboriginal cultures in this territory of Labrador being ignored. This more or less puts the pressure on truth and reconciliation to be, in fact, truth and reconciliation.

"The honeymoon is over, as somebody said, and now the rubber hits the road."

Nalcor Energy said early Thursday that project opponents blocked access to the Muskrat Falls construction site near Happy Valley-Goose Bay, preventing workers from getting in.

Spokeswoman Karen O'Neill said the blockade affected the day shift but didn't indicate what action may be taken. She confirmed essential work inside was going ahead.

About 80 protesters in Labrador rebuked the terms of a court injunction earlier this week by crossing the Trans-Labrador Highway to block the Muskrat Falls gate. They're protesting what they feel is improper preparation of the flood zone for the hydroelectric project, fearing possible methylmercury poisoning in the area's wildlife. (Katie Breen/CBC)

The troubled project is already beset by cost overruns, delays and a price tag that with financing has soared to $11.4 billion from $7.4 billion four years ago.

First power is now expected to flow in 2019 instead of sometime next year.

Those who barred the site entrance Thursday defied a court injunction Nalcor obtained earlier this week against obstruction of its main entrance, leading to the arrests Monday of nine people.

The new, larger blockade started hours after Nalcor confirmed Wednesday that methylmercury levels are expected to rise in the 41-square-kilometre reservoir created by the dam. About 2,000 Inuit who live downstream from Muskrat Falls rely on fish and seal meat as food staples.

Workers at the Muskrat Falls site were allowed to leave but protesters stopped them from entering on Thursday morning. 0:50

The provincial government has ordered Nalcor to remove more forest cover from the land that will be flooded amid fears of methylmercury contamination if too many trees are left to rot under water.

Learning said it's not nearly enough.

"The real methylmercury is (created from) the ground itself. They can take every tree from around the shore, it would mean nothing until they've dug up the moss down to the sand."

Nalcor, however, has indicated it plans to begin initial flooding — about 25 per cent of the total reservoir — later this month.

Learning said support from Wabush, Cartright and other parts of Labrador is expected to create an even larger blockade late Thursday. He hopes for a peaceful show of united opposition without injuries.

"I'm sure the police will use their discretion and, as we grow in numbers, they will step back."

Justin Trudeau hugs Elder Evelyn Commanda-Dewache, a residential school survivor, during the closing ceremony of the Indian Residential Schools Truth and Reconciliation Commission, at Rideau Hall in Ottawa on Wednesday, June 3, 2015. (Sean Kilpatrick/The Canadian Press)

A request for comment Thursday from the Prime Minister's Office was deferred to Fisheries Minister Dominic LeBlanc.

"Our government is committed to a renewed nation-to-nation relationship with indigenous peoples based on recognition of rights, respect, co-operation and partnership," he said in a statement.

Labrador Liberal MP Yvonne Jones, parliamentary secretary to the minister of indigenous affairs, has said she wants Premier Dwight Ball and Nalcor to hold more talks with residents before any flooding.

She also called for a review to ensure environmental conditions as part of federal permits are being met.

But the LeBlanc statement puts the ball back in the provincial court.

"We expect the province will meet its responsibilities to ensure the health and safety of Canadians."

Children protesters and Muskrat Falls workers separated by a gate on Wednesday. The protests have disrupted work at the site just as flooding of the reservoir was scheduled to begin. (Katie Breen/CBC)

Charlie Angus, the federal NDP critic for Indigenous and Northern Affairs, said the Liberal government isn't living up to Trudeau's promise of "real and positive change" for aboriginal people.

"There are obvious issues in terms of the environmental threat for mercury poisoning," Angus said in an interview. "They're ignoring that.

"First Nation people were expecting this new relationship of respect and commitment from the government. And the government is trying to walk away on it."

Dozens of supporters from the provincial and Canadian arts and culture sectors on Thursday signed a letter in support of those trying "to halt the negligent flooding of the Muskrat Falls reservoir."

Those who signed — including Jillian Keiley, artistic director of English theatre for the National Arts Centre in Ottawa, and "February" author Lisa Moore — specifically named Billy Gauthier. The Inuk artist from North West River in Labrador has now been on a hunger strike for a week to demand full clearing of the reservoir.

Maude Barlow, national chairperson of the Council of Canadians, said what was once a regional fight is going national.

"People are realizing that these megaprojects are bad for the environment. They're the wrong way to go," she said in an interview.

"I think you're going to find that Muskrat Falls becomes a real symbol of everything that's wrong with the way we exploit our resources, to the benefit of a few corporate investors, and put the lives and livelihoods of people at risk."