LONDON, ON -- Spooked by native and Occupy protests, the National Energy Board has barred citizens from a hearing that could remove obstacles to bringing oil to Southwestern Ontaro from Alberta's oilsands.

"It is unfortunate today that we have to take this step," board chair Roland George said Wednesday. "(Protesters) have not shown respect and caused serious concerns about the safety of those in attendance."

Only media and groups that applied earlier to intervene in the issue will be allowed in the hearing room Thursday at Hilton London -- others can only tune in to a live webcast.

Earlier Wednesday, moments before pipeline giant Enbridge was to speak to the board, protesters brought the hearing to a halt, rising to their feet, a leader bellowing out at the injustices and others repeating phrases as if at a revival.

Board members fled the room as members of the Aamjiwnaang First Nation decried what they called an intrusion on their lands and treaty rights.

"We're fed up with this," said one native woman. She said her name is Yagotala and that she's part of the Mohawk Nation. "The government isn't listening."

A board official, with police backing him, ordered the room cleared and nearly all left without incident, but one woman was arrested.

The hearing resumed later with police monitoring who could enter the room.

First to speak was Enbridge, which wants to reverse the flow of oil in a pipeline in London's backyard so it moves from west to east, from Sarnia, Ont., to Westover, ON, near Hamilton, ON.

Less reliable oil from overseas can be replaced by Alberta crude, Enbridge lawyer Douglas Crowther told the energy board. "This will benefit shippers, producers and the broader Canadian public interest."

He disputes claims by environmentalists, who point to a rupture of an Enbridge pipeline in Michigan two years ago and say Londoners should be alarmed because the pipeline crosses under the Thames River just north of the city.

The involvement of the Aamjiwnaang First Nation was not limited to the protest -- its chief and its lawyer argued Enbridge had done far too little to establish the changes it plans are safe for the environment or respect treaty rights.

There's been no oil in the pipeline this year and only a trickle last year, so Enbridge must show if increased flow will denigrate the air, water and soil, lawyer Scott Smith told the board.

Then the company must share findings with and seek input from Aamjiwnaang First Nation, he said.

Instead, Enbridge has only studied some of the changes and addition to its infrastructure, he said.

Environmentalists fear Enbridge's push to reverse the flow of oil near London is the first step toward moving oil to the U.S. East Coast, a move that could speed oilsands production and degrade the global environment.

Some environmental groups will make their case Thursday.

Margaret Vance, president of the Ontario Pipeline Landowners Association, has immediate concerns: the pipeline is within two kilometres of her farm north of Woodstock, ON.

"I don't want to walk out on our backyard and see a field of oil," she said.