Workers on the Muskrat Falls project say they were blocked from leaving the site Tuesday evening and demonstrators are vowing not to let anyone into the site.

"Traffic can come out at a normal flow but we're not letting any traffic back in," said Jim Learning, a protester at the site.

Busses coming out but no vehicles being let in to <a href="https://twitter.com/hashtag/muskratfalls?src=hash">#muskratfalls</a> site <a href="https://twitter.com/hashtag/cbcnl?src=hash">#cbcnl</a> <a href="https://t.co/VDpwYrze1H">pic.twitter.com/VDpwYrze1H</a> —@JacobBarkerCBC

Learning was not concerned by the police presence and was "absolutely" prepared to be arrested Tuesday evening.

"We have to make our point that is the only thing, we can't hurt anybody, we're not going to hurt anybody, we can't push back any other way except throw ourselves on the line," he said.

Jim Learning stood outside the Muskrat Falls site in protest of the megaproject Tuesday evening. (Bailey White/CBC)

The Labrador Land Protectors issued a call for supporters on Tuesday evening to gather at the gate for a "peaceful action."

Workers with the project said it was protesters who blocked the main gate, reportedly preventing employees from leaving. People complained of being stuck on buses sweating it out for about an hour in Labrador's 30 degree-plus heat at the end of their work day.

Police were on site outside the Muskrat Falls gate Tuesday monitoring the protest. (Bailey White/CBC)

Both supporters and opponents of the megaproject took to social media to express their frustration — and tensions quickly flared between the two sides.

"Employees are soon gonna fight back. And I guarantee that we out number them. Let's start a brawl," wrote one person on Facebook, who said the sweltering conditions onboard the buses were too much to handle, after a 12-hour shift.

"The 'land protectors' clearly don't have the health and safety of these poor people who are stuck on the bus in mind," wrote another person.

At least some of the workers were eventually permitted to exit the gate via bus, but the 12 to 15 protestors were not permitting anyone to enter — and seven demonstrators physically blocked traffic.

Outgoing traffic was blocked for about an hour so around 7PM workers like Matt Pomeroy and Derek Russell left on foot <a href="https://twitter.com/hashtag/cbcnl?src=hash">#cbcnl</a> <a href="https://t.co/IOuCC8HHAu">pic.twitter.com/IOuCC8HHAu</a> —@baileywhite

But the Labrador Land Protectors insisted it wasn't their supporters that blocked the way.

"It was security that locked the gate and would not let workers leave. Not the Labrador Land protectors," the group wrote on its Facebook page.

Opponents of the project say the efforts must be maintained to halt the project.

"Nothing good will come out of Muskrat Falls. The dam will break and lives will be lost. Just a matter of time," one woman wrote.

The first barge carrying 4 of 7 transformers for the Muskrat Falls site has departed Bay Bulls to begin its marine journey to Cartwright! <a href="https://t.co/b0Bk4TAvzx">pic.twitter.com/b0Bk4TAvzx</a> —@NalcorEnergy

Protesters chose Tuesday for their demonstration, knowing the turn around schedule of workers, with plans to prevent the next shift from entering the work site.

Protest spurred by shipment of electrical transformers

The latest protest was spurred by the start of the trek of seven 200-tonne electrical transformers, which are headed to the Muskrat Falls site.

Nalcor had hoped to move the transformers last fall, but residents voted at a public meeting in November to stop the move in a dispute over how much soil and vegetation would be removed from the Muskrat Falls reservoir.

Another issue protestors have been focusing on for months is calling for Nalcor to clear a nearby reservoir of vegetation and topsoil before flooding.