PSNI officer. Pic Colm Lenaghan/Pacemaker

A source told this newspaper that steam was in fact rising from the roof and officers had suspected that the building might have been a cannabis factory, where heat and artificial light are required to grow plants year-round.

The officers reported their suspicions to their superiors, who requested and obtained a search warrant to inspect the premises.

However, when police entered the shed they found that it was almost entirely empty – but that the heating was running.

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A source with knowledge of the incident told the News Letter that the owner of the premises had admitted that he was running boilers in the empty building because it was making him money, but said there was nothing illegal taking place and police therefore left the scene because there was no longer any concern about a drugs link.

Meanwhile, in a separate development the Ulster Unionist Party yesterday formally asked the PSNI to investigate the entire RHI situation. UUP MLA Steve Aiken said: “I have written to the Chief Constable of the PSNI on foot of assertions made by the Minister for the Economy at yesterday’s emergency Economy Committee meeting.

“At that meeting – which was called at my behest in the absence of the Sinn Fein chair and members of the committee – Simon Hamilton did not contest the suggestion that there was criminal intent on behalf of some beneficiaries of the RHI schemes. He went on to confirm that fraud had been detected in the inspections which are currently being carried out.

“However, when I asked if the PSNI was involved in investigating these allegations, I was surprised to be told ‘not yet’.