A court has ordered a fresh investigation into what caused an explosion at an embattled Queensland power station, which left almost half a million people without power.

In a Federal Court judgement handed down on Monday afternoon, the court ordered IG Power appoint special administrators with powers to complete a new investigation into the incidents at the Callide Power Station, near Biloela.

Czech business Sev.en, an investor in IG Power, had sought special administrators John Richard Park and Benjamin Peter Campbell of FTI Consulting be appointed to investigate the cause of the explosion and a separate cooling tower collapse.

In May 2021, an explosion at the C4 unit caused widespread blackouts to 470,000 properties across Queensland.

While the Queensland government-owned CS Energy engaged forensic engineer Sean Brady to conduct an independent investigation into the C4 unit, almost three years after the incident the report has still not been released.

In November 2022, a part of the cooling tower in the C3 unit also collapsed and both the C3 and C4 units remain offline. 

Justice Sarah Derrington ordered investigations be conducted into the two incidents by a suitably qualified expert.

She has also granted access to books and records necessary for the purpose of the investigation.

Who pays for the additional investigators will be determined at a later date.

Voluntary administrators were appointed to IG Power in March last year.

CS Energy owns Callide C in a joint 50/50 venture with IG Power. 

Both C3 and C4 units remain offline and while work has been done to return them to service, both have been plagued by delays.

CS Energy said earlier this month the C3 unit will return to service by the end of March, while the C4 unit is expected to come fully online by the end of July.