Anti-seal hunt activists have accused the Canadian authorities of preventing them from carrying out their role as observers of the annual cull.
Hunters have taken fewer seals this year so far than previously
Seven activists were arrested on Sunday for getting too close to some hunters. They were later released, but insist their boat was rammed by the hunters.
US Humane Society members say they have now been grounded and their film seized while an investigation is carried out.
Canada insists the cull of 325,000 harp seal pups is needed to control numbers.
But there has been an international outcry, with celebrities such as Sir Paul McCartney and Brigitte Bardot joining protesters describing the cull as barbaric and unnecessary.
There were angry confrontations between activists and sealers as the hunt got under way at the weekend in the Gulf of St Lawrence region in Quebec.
At one point, a sealer flung the carcass of a skinned seal at an inflatable craft carrying protesters and journalists.
Canada's fisheries department says seven activists were arrested because their boat violated a condition that it stay at least 10 metres away from the hunters.
But Rebecca Aldworth of the US Humane Society insists the hunters had deliberately veered their vessel into them.
Found in north Atlantic and Arctic oceans
Feed on fish and crustaceans and spend much of year at sea
Pups born on the ice and nursed for two weeks, after which their mothers abandon them
Can be legally hunted only once their white coats darken, at about two-weeks-old
"We did not violate any law. It was a deliberate act. They want us to leave the area," she said.
She said video footage from Sunday had been confiscated and they have been banned from returning to the ice floes while an investigation is under way.
"This was a calculated attempt by Canadian officials to keep observers from documenting the hunt," she said.
Roger Simon of the fisheries department said an investigation into whether to bring charges was under way, but admitted it is "a long process."
He said the activists could still apply for observer permits, which are renewed on a daily basis, but conceded that the current inquiry would be a factor in deciding whether to give approval.
Fall in numbers
The cull, which reportedly earns C$16.5m (£8.3m) in meat and pelt sales, is an important source of income for fishing communities in Quebec and Newfoundland that have been hit hard by dwindling fish stocks in the Atlantic.
The Canadian government increased the total allowable catch this year, saying the seal population is now almost six million, nearly triple the level of the 1970s.
Prime Minister Stephen Harper has insisted the cull will be carried out humanely and said Canada was victim of an "international propaganda campaign".
Some 90,000 seal pups are expected to be culled in the Gulf of St Lawrence, before the hunt moves on to Newfoundland, where thousands more will be culled.
But the hunters have been frustrated by a huge fall in the number of seals they have taken in comparison to previous years because of thinning ice caused by warm weather.