Protesters from Greenpeace occupied two dump trucks and unfurled a banner on the ground at Shell's Albian Sands oilsands site in northern Alberta Tuesday. (Greenpeace)

A group of Greenpeace activists chained themselves to a three-storey dump truck and surrounded it with pickup trucks at Shell's Albian Sands mine about 80 kilometres north of Fort McMurray, Alta., Tuesday morning.

The protest was launched by the environmental group in advance of Prime Minister Stephen Harper's meeting with U.S. President Barack Obama in Washington, D.C., Wednesday.

"We definitely … want to send a strong message to President Obama and Prime Minster Harper tomorrow that climate leaders don't buy tar sands and so … we're planning to stay here as long as it takes to get that message across," said Mike Hudema, a Greenpeace activist from Edmonton who is at the site.

Protesters from Canada, the United States and France entered the site at 8 a.m. MT.

They blockaded the giant truck and shovel by chaining the pickup trucks together. They then chained themselves to the larger truck while a second group placed giant banners on the ground that say: "Tar Sands: Climate Crime."

In an email update late Tuesday afternoon, a Greenpeace spokesperson said the protesters occupied a second dumptruck on the site and have no plans to leave.

Shell temporarily suspended operations at part of the Muskeg River mine over safety concerns for the protesters, company spokesperson Paul Hagel said. By late Tuesday afternoon, Shell was working to get most of the site back into production, he said.

Company says it's trying to 'reach out' to protesters

Hagel said there is "significant" security at the site, so it is not clear how the protesters were able to gain access. Right now, the company is trying to determine what they want.

"Our goal is just to reach out to them, try and understand what they're looking for and we'll determine at a later juncture if [there'll] be legal action taken," he said.

Reports of how many protesters there are have varied. In a news release, Greenpeace said 25 people are taking part in the protest but RCMP said they've seen about 12 to 15.

RCMP spokesperson Const. Karolina Malik didn't have many details about the situation but she confirmed police are there.

"We are working with Albian Sands security right now," she said.

In July 2008, 11 Greenpeace activists were arrested and charged with trespassing after they tried to block a pipeline dumping tailings waste into a tailings pond at Syncrude Canada's Aurora oilsands site.