The lack of communication between civil servants over the funding of the bungled Renewable Heat Incentive was "almost surreal", the chairman of the inquiry into the scheme has said.
In another day of evidence at the inquiry, the Department for Enterprise, Trade and Investment (Deti) came under severe criticism from Sir Patrick Coghlin, the former judge chairing the probe.
Sir Patrick described as "almost surreal" a catalogue of blunders and communications failures by the Northern Ireland civil servants tasked with looking after the botched scheme, which is set to cost the taxpayer millions of pounds.
The failed RHI scheme was set up in 2012 with the aim of encouraging businesses to switch to green energy.
But a crucial lack of cost control measures left it open to abuse, with applicants able to earn money by burning more fuel than they needed.
When it collapsed in late 2015, it was feared the public would be faced with an overspend bill of nearly £500m.
Yesterday's hearing heard how civil servants had given chicken processing firm Moy Park - now owned by American poultry giant Pilgrim's Pride - early warning of proposed changes to the RHI funding scheme that could have made it even more lucrative for applicants.
Moy Park's suppliers were among the biggest users of the RHI, which encouraged firms and farms to switch to biomass heating systems.
An internal Moy Park email which had been furnished to the inquiry showed that the company was aware Deti's energy team had changed its cost control plans for the RHI scheme from proposals which had gone to public consultation in 2013.
Deti was also considering proposals to introduce a 'district heating' tariff, which would have paid a higher subsidy to scheme members.
Sir Patrick asked who had made the decision for that policy change, and asked why it had been made known to a company which was one of the biggest users of the scheme after the public had been consulted on a completely different system.
Civil servants from Deti also told the inquiry that they did not tell their then minister, Arlene Foster, about changes which were made to the RHI scheme after she had already signed it off.
The hearing also heard from Deti civil servant Seamus Hughes.
It was Mr Hughes' job to manage the day-to-day running of the scheme in 2014.
He had no experience of the scheme when he joined the Deti's 'energy team' in 2014.
In an earlier appearance before the inquiry, he said he "didn't understand what was going on".
Yesterday, Mr Hughes disputed an account of a meeting he had with Dr Edmund Ward of Ofgem about the running of the RHI scheme.
Mr Ward has told the inquiry that he had discussed the issue of cost controls on the RHI scheme with Mr Hughes - a claim Mr Hughes rejected.
However, when inquiry panel member Dame Una O'Brien - a former Permanent Secretary at the Dep artment of Health (DH) in London - asked if a minute had been taken of the disputed meeting, it was learned that no minutes of the disputed meeting had been kept.