Leaking chemicals, a disintegrating asbestos roof and crumbling structures are among the list of concerns recently raised by authorities looking into Clive Palmer's nickel refinery near Townsville in north Queensland.

Key points: The Yabulu site has been in caretaker-maintainer mode since 2016

The Yabulu site has been in caretaker-maintainer mode since 2016 WHSQ found other issues across two subsequent investigations in 2017 and 2018

WHSQ found other issues across two subsequent investigations in 2017 and 2018 In a statement to ABC News, Clive Palmer said operators have been working with authorities in accordance to workplace laws

The safety issues are detailed in three separate reports commissioned by the Queensland Government since the refinery's financial collapse in early 2016.

It comes in addition to revelations of a dangerous explosion at the site and fears about the structural integrity of the refinery's concrete stack, as revealed by ABC's 7.30 this week.

The site has been in caretaker-maintainer mode since 2016.

One of the reports, carried out by private engineering firm WorleyParsons in 2016 on behalf of Workplace Health and Safety Queensland (WHSQ), found structures at the refinery visually corroded and deteriorated amid chemical leaks.

An aerator tank leak has caused corrosion at the refinery. ( WorleyParsons 2016 report )

"High levels of chemical residue and leakage had accumulated over several structures and equipment," the report said.

"A general pattern of severe corrosion was observed around those areas exposed to high levels of sulphur … exhibiting extremely severe structural corrosion and concrete cancer."

It also found degraded staircases and handrails — and parts of an asbestos roof — had caved in on one of the key buildings, allowing rain to come in and pool on the floor.

Concrete degradation exposes steel at the refinery. ( WorleyParsons 2016 report )

WHSQ found other issues across two subsequent investigations in 2017 and 2018.

In its latest inquiry, while WHSQ acknowledged some pipes and structural supports had been repaired, other issues were left outstanding.

Report identifies failure of asbestos roof sheeting as shown at the refinery. ( WorleyParsons 2016 report )

Inspectors found fire clearings had not been kept, emergency showers were disconnected from water sources, fire extinguishers had not been maintained for almost two years, and loose cladding was posing a safety risk if the site was ever to be affected by a cyclone.

A Workplace Health and Safety spokesman said the refinery has been issued with at least 22 improvement notices for significant workplace breaches since 2016 — all of which have since been rectified.

Bent knee brace at the refinery at Yabulu. ( WorleyParsons 2016 report )

In a statement to ABC News, Mr Palmer said operators had been working with authorities in accordance to workplace laws.

"At all times Queensland Nickel Sales Pty Ltd, the current manager of the refinery, has been compliant with the act and has continued to work with the relevant authorities to ensure that the Refinery is safe and compliant," Mr Palmer said in the statement.