After a half-hour struggle, they managed to remove the chain from the table, and took the four off with the chains still around their waists.
Protesters had been handcuffed as well, and were told they would be charged with mischief.
Ontario Power Generation, or OPG, wants to build new reactors at the Darlington site.
Greenpeace spokesman Shawn-Patrick Stensil said the protest had drawn attention to what the group considers to be inadequacies in the hearings.
“We don’t want these hearings to be used as a promotion for OPG’s project,” said Stensil.
“This process shouldn’t be used to legitimate that project.”
Environmentalists had asked the panel to adjourn the hearings until more information is gathered about the Japanese nuclear disaster, but the panel refused.
"They won't look at a Fukushima-scale accident," Stensil said of the panel.
He noted that China and Switzerland have suspended their nuclear processes.
The demonstrations began at around 9 a.m. that day by nine protesters, four of whom chained themselves to the table at the front of the room in a church in Courtice where the hearings were scheduled. The other five agreed to move to the back of the room.
Although the protest wasnÂ’t physically preventing the hearings from proceeding, Chairman Alan Graham called an adjournment when he asked them to move and they quietly refused.
By around noon, a hearing official formally requested police to clear the hall of anyone disrupting the hearings.
Police then gave the protestors one more chance, asking them to leave voluntarily, but all refused.
ThatÂ’s when the police took action.
The protestors had previously been warned that they would be arrested and charged with mischief if they didn't leave but they held their ground.
“We're continuing to disrupt the hearings that are happening today that we feel are unjust, especially given the situation that's happening in Japan,” Laura Severinac, one of the four, said earlier.
“We feel that nuclear energy is dirty, dangerous and expensive and we want these hearings suspended.”
“We're not prepared to leave until they stop the hearing,” said Alex Speers-Roesch, another one of the four.