Work began Thursday on a controversial plan to realign the Trans-Canada Highway west of Charlottetown, but protesters appeared on the site and RCMP shut the project down for the day.
Police said the work site required fencing to keep protesters at a safe distance.
"It wasn't a safe work environment because some of the individuals who were protesting actually went down right on to the work site," said RCMP Sgt. Andrew Blackadar. "The contractor has to maintain a safe working site and we asked them to suspend their work."
Environmental approval was granted for the project — which would straighten out the highway in the New Haven-Bonshaw area — on Monday, and tree clearing began early Thursday morning.
One of the protesters, Cindy Richards, spoke to CBC News before RCMP shut the site down.
"They are taking trees down," said Richards.
"I have seen tears. I've seen anger. They are not following their own rules and it is very frustrating. It is frustrating to watch these large trees fall into the ground when there is no rhyme nor reason behind it yet."
There were only about 10 protesters at the work site. RCMP made the call to shut it down at about 1 p.m. Kim Horrelt, provincial director of infrastructure, said she expected fencing would be up Friday so that work could continue.
Representatives for the protesters told CBC News they were caught by surprise by the start of work, and they expect to be able to mount a larger protest on Friday if construction resumes.
"It really is an exercise in democracy for us," said protester Roy Johnstone. "We feel the Premier hasn't listened to the concerns of tens of thousands of Islanders over this issue."
The province has started a newspaper and radio ad campaign outlining the new route and why it feels the highway must be changed for safety reasons.