Monk later said in a statement that the protestors would let the Department of Conversation and "anyone who needs to do safety work" through the barricade, "but sealing up the mine isn't going to happen".
"Solid Energy and the Government have tried to ignore us and push us aside. Now they have to listen to us."
The protestors will head to Wellington to petition the new Prime Minister Bill English on Tuesday, his first day in office, to halt the sealing of the mine and present a new expert re-entry plan to him, Monk said.
"Pike River is a crime-scene and we want to get into the drift to recover our loved ones' remains and the evidence that might be down there. We've got a plan to do it and we're not going to let the opportunity to get answers get buried under hundreds of tons of concrete."
The disaster
An explosion at the mine in November 2011 claimed the lives of 29 men who were inside. Their bodies are yet to be recovered.
The Government, along with representatives from Solid Energy, concluded it was safe to go back inside the mine in 2013, but 18 months later Solid Energy did a U-turn, stating re-entry would claim more lives.
But many of the victims' families disagreed, citing independent experts who said it was still safe to re-enter. They have been protesting against Solid Energy's decision to seal the mine's entrance.