The Avengers star Mark Ruffalo has become the latest big name to back the protesters battling to stop oil drilling at Woodburn Forest in Co Antrim over fears of water contamination.
In a letter to Environment Minister Mark H Durkan, the Water Defence founder, who plays The Hulk in the Marvel movies, said the clean water advocacy group would be sending water-testing kits to local residents.
"We implore you to protect your citizens by protecting their water," Mr Ruffalo wrote. "The small amount of oil and gas that can be extracted from that site pales in comparison to the nightmare that contaminating the water supply for over 131,000 residents in your community would cause."
This week protesters including residents and Stop The Drill campaigners reacted angrily after InfraStrata began felling trees in preparation for drilling, even though no waste management plan has been approved.
The firm has been granted a licence to drill an exploratory borehole for oil and gas under permitted development rights after the Department of the Environment (DoE) did not deem it necessary to require planning permission.
Mr Ruffalo said it was troubling that the DoE was not intervening to stop an activity that appeared to be unlawful because of the lack of an approved waste management plan and alleged inadequate assessment of environmental considerations.
"It is extraordinary that on this sensitive site there has been no public scrutiny through the planning process and no environmental impact assessment," he wrote.
But Northern Ireland Water claimed it was satisfied that the proposed work would have no detrimental impact upon the nearby reservoir or the public water supply.
"If a spill into the catchment was to occur and enter surface watercourses to any of the Woodburn reservoirs, then NI Water has the ability to isolate the reservoir and cease abstraction from the reservoir," it added.
InfraStrata, meanwhile, insisted the worksite had been designed to ensure the maximum level of environmental protection.
A spokeswoman said: "This will involve the development of a fully watertight site surrounded by a high bund which will contain all fluids, including rainwater, within the site. (It is) lined with a specialised geosynthetic clay liner which prevents any liquids onsite from penetrating into the ground below, thereby protecting local watercourses and ensuring there will be no adverse impact on the Woodburn River and dams catchment.
"The borehole itself will be lined with multiple layers of steel casing and cement to protect the surrounding ground.
"NI Water is satisfied that the proposed works will have no detrimental impact on the public water supply.
"In any event, a strict regime of water monitoring has been agreed with the Northern Ireland Environment Agency."
Motorcycle road racer Glenn Irwin is also backing the protest and has been picketing the site since last Wednesday.