A Toronto woman was among those arrested on the second day of a mass protest held outside the White House to denounce a planned pipeline that would transport Canadian oil from Alberta to Texas.

Dozens of protesters were removed by U.S. Park Police on Sunday for failing to obey orders governing demonstrations on the grounds of the White House.

Patricia Warwick, 68, of Toronto, and a 65-year-old woman from Massachusetts were arrested shortly before noon and by the end of the day about 50 people had been detained. U.S. Park Police Sgt. David Schlosser said late Sunday everyone arrested was later released.

On Saturday, police arrested 50 demonstrators during the first day in a two-week series of sit-ins to denounce the proposed pipeline that would transport crude from Alberta's oilsands to a refinery in Texas. According to Schlosser, activists jailed Saturday will likely be released late Monday. A number of reasons could account for the delay, he said, including previous arrests or inadequate identification.

Outspoken environmentalist and protest organizer Bill McKibben and notable gay rights activist Dan Choi were among those arrested during the protest's first day.

Protest organizers from Tar Sands Action say they had been told demonstrators would be arrested and then released with a warning, but protesters are instead being charged and held in jail for two nights.

Daniel Kessler, a spokesperson for the group, said he has been told by police that they are keeping some activists in jail "as a deterrent."

According to Kessler, because the Martin Luther King Jr. memorial is scheduled to be unveiled on the National Mall this coming Saturday, police are trying to preserve the peace ahead of those festivities.

"Which is ironic because these are peaceful demonstrations, and exactly the type of protests that Martin Luther King advocated," Kessler said.

The demonstration, which is expected to run until Sept. 3, comes as the U.S. State Department prepares to release its final environmental analysis of TransCanada's Keystone XL pipeline.

The State Department is tasked with making a decision on the pipeline because it crosses an international border. After it produces its assessment, President Barack Obama will have 90 days to determine whether approving the $7 billion pipeline is in his country's national interest.

Jane Kleeb, an environmental activist, told CTV News Channel on Sunday that when the protestors first started demonstrating they believed they had a five per cent chance of convincing the government that the project should be nixed.

But Kleeb said she is now more optimistic that their efforts may prove successful.

"We know how powerful big oil is in the States and in Canada, but there has been very sustained community and grassroots donors who are really pushing back on this and I think we have a 50/50 shot," she said. "We're telling Obama that we are serious and there is a serious risk facing our communities."

Obama is currently on vacation with his family over 780 kilometres away from the White House in Martha's Vineyard. The Obama family is expected to return to Washington late next week.

Environmentalists have condemned the Alberta oilsands, accusing them of being the world's biggest emitter of carbon and responsible for so-called "dirty" oil.

Alberta Environment spokesperson Mark Cooper has brushed off the suggestions that the oilsands emit excessive amounts of carbon, accusing the coal industry of being far dirtier.

In 2009, a single coal plant in China produced roughly the same greenhouse gas emissions as the entire oilsands industry, he said on Saturday.

Kleeb said many people in Nebraska, one of the states the pipeline would snake through, are concerned about their drinking water if the pipeline were to leak oil.

She said the activists would rather see a shift in energy sources.

"We want to see more sustainable energy," she said. "We think that will bring long-term economic benefits instead of a short-term gain."

Sit-in organizers said Sunday they expect more protesters to join them on Monday, including a group of farmers and ranchers from Nebraska. On Sunday, protesters included a group of doctors from Chesapeake Physicians for Social Responsibility.

Supporters of the oil and gas industry also stress that the proposed pipeline project will create jobs, which will provide a boost to the economy.

With files from The Associated Press