Checks are still being carried out on some of the companies involved in a controversial exploration for oil at Woodburn Forest - even though work on the site has already started.
Campaigners from the Stop The Drill protest group say it is "outrageous" that InfraStrata is pressing ahead with work on the Co Antrim well site close to a drinking water reservoir before a Stormont department has determined whether its consortium partners have the ability to do the work or restore the site.
The group tweeted a letter from the Department of Enterprise, Trade and Investment which revealed that it is still considering a request from InfraStrata to have a number of companies added to its licence.
The letter said: "Due diligence by the Department is ongoing and accordingly DETI's consent to the proposed assignments ... cannot be confirmed until the outcome of DETI's due diligence processes is known."
Drilling close to Woodburn Reservoir, which supplies drinking water to thousands of homes across Belfast and Co Antrim, is expected to start in May.
Opponents, including residents living near the Carrickfergus forest, claim chemicals used in the drill could pollute the water table of Woodburn Reservoir.
Their campaign has been backed by Spotlight and Marvel Avengers star Mark Ruffalo and human rights advocate Bianca Jagger.
Last night, Stop The Drill campaigner Majella McCarron said it was "outrageous" that work has gone ahead without due diligence checks being completed.
"They are in the forest trashing it and DETI still doesn't know if they are financially or technically able to do the job or restore the forest," she said.
"Due diligence should have been done before the company went on site."
A local resident has put Mid and East Antrim Borough Council on notice of his intention to commence judicial review proceedings against the decision to grant leave to the project.
Last night, DETI said consent for the work being undertaken to date by InfraStrata and the issues addressed in its letter were separate matters.
It said the latter was "concerned with the matter of 'assignment' of rights/interest shares in the licence".
And it added: "DETI's consent to the assignment of any right under the licence is required before that assignment can take effect but the terms of the licence are not designed to interfere with commercial companies' rights to freedom of contract nor to inhibit the carrying on of activities for which appropriate approvals are in place."
The department confirmed that InfraStrata wrote to DETI on February 5 seeking written consent for the assignment of "various revised interests" in its Petroleum Licence.
The spokesperson added: "Due diligence by DETI officials is currently being finalised. The next steps are for DETI to notify the licensees of the outcome."
It comes after InfraStrata confirmed that it was responsible for an oil spill at Woodburn Forest over the Easter weekend - the second reported leakage.
The Department of the Environment said an inspection was carried out by NIEA on Easter Monday and evidence was found of a very minor mineral oil spillage which had entered a small waterway running across the site.
"The inspector confirmed the presence of some surface oil sheening in the area that would be consistent with the loss of a minor volume of fuel or hydraulic oil," a spokesperson said.
Meanwhile, Environment Agency inspectors have been ordered to carry out a visit to the site "to identify if there are any potential pollution sources or risks associated with the current activities on the site".