Around 20 senior citizens have put the Queensland's government headquarters into lockdown as they protested against the Adani coal mine.
The protesters allege Adani breached its pollution licence by releasing toxic coal sludge into wetlands near the Great Barrier Reef during Cyclone Debbie last year and are demanding the state government prosecute the company.
The group entered the building's foyer with hidden banners at around 11am on Monday .
About ten police then negotiated with the group and after about an hour and a half the senior citizens quietly left the building.
Galilee Blockade spokesman Ben Pennings says after the protest the group met with top public servants and discussed the alleged licence breach.
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"They were in strong agreeance with us that Adani and all facilities need to be ready for storms and cyclones," Mr Pennings told AAP.
"Adani obviously wasn't (ready) because of the release of the toxic coal sludge."
He said the government had confirmed it was still investigating Adani and would announce the outcome before the September 7 deadline.
Liberal National Party Opposition Leader Deb Frecklington said the government should investigate whether any breach had been covered up, but said the project needed to proceed.
"We know that the environmental approvals are all in place and Adani needs to get going so that those jobs they've promised for regional Queensland start," she said.
"In relation to any prosecutions, that's up to the government to monitor and carry out as they should."
Environment and Great Barrier Reef Minister Leeanne Enoch did not meet with the protesters on Monday, but issued a statement saying she understood it was an "issue people care deeply about."
"This is a matter for the Department of Environment and Science as the regulator, and remains under formal consideration," the minister said.
