A massive fire that burned for days at a government medical supplies warehouse in Berrimah was caused by a “malfunction of an electrical item”, investigators said on Friday.

The blaze began on August 23 and had taken fire crews hours to get under control and continued to smoulder until earlier this week, destroying millions of dollars worth of medical supplies.

It was reported at the time that oxygen tanks exploded in the fire, along with other medical supplies, while crews raced to move nearby fuel tanks from the immediate area.

NT Fire and Rescue services said investigators had limited access inside the building in the early stages due to “structural instability”, after the majority of the building was damaged and a large part of the roof collapsing.

On Friday, Acting Deputy Chief Fire Officer Joshua Fischer said investigators believe there “are no suspicious circumstances surround the fire with the determined cause being accidental”.

“The source of the fire was a malfunction of an electrical item,” he said.

It was not explained what that item was.

Mr Fischer also did not provide comment on whether the building required a functioning sprinkler system.

Public records show the non-descript Berrimah building on College Road that caught fire is owned by Moranidini Earthworks Pty Ltd and was leased to the NT Government in possibly November 2018 for annual rent of slightly more than $356,000 and was set to expire in October 2024, with options to extend.

It is still unclear if the building was one of the more than 300 government-owned or leased properties the ICAC is currently investigating for failing to have proper certification.

Mr Fischer did not mention that in the statement and thanked staff for combatting the blaze.

“I’d like to thank our JESCC staff who received numerous calls regarding the incident and our career firefighters who worked tirelessly to protect neighbouring assets so that the fire did not spread,” he said.

The fire left Health Department officials scrambling to replace the lost medical supplies.