Four young people were seen entering a derelict building in central Wellington yesterday shortly before it caught ablaze, police say.

Flames as high as 20m were seen as the empty building on Ghuznee St, near the intersection with Cuba St, spewed heavy smoke on Sunday afternoon.

The heritage-listed Ghuznee St building is Toomath’s, which was cordoned off as an earthquake risk in 2019. Nearby retailers have voiced their fears the fragile building would collapse in a quake.

Today police said they wanted to speak to witnesses of the fire, especially four young people seen going into the building before the blaze started.

 “Police have been working with [Fire and Emergency New Zealand] this morning and are satisfied that no one was trapped in the building during the fire,” police said in a statement.

Crowds of people gathered to watch the fire. Photo / George Heard

“The cause of the fire is not yet known and inquiries are under way to establish how it started.

“The building has sustained serious structural damage and it has now been handed over to the Wellington City Council who are commencing demolition.”

Police received reports of four young people - three boys and one girl - aged about 10-15 years old jumping the fence at the back of the building shortly before the fire.

They were last seen in Cuba Mall around 2.20pm on Sunday. The first report of the fire came about 10 minutes later.

 “Police also understand people have been accessing the building from the Wilsons carpark in the days before the fire and would like to speak to anyone that has knowledge of this or who may have seen anything suspicious in the area, particularly between 1.30-2.30pm Sunday 15 October.”

A Wellington City Council spokesperson said fire investigators had been unable to gain access to the building due to its “unstable nature”.

“A New Zealand Urban Search and Rescue team used drone footage to get some preliminary visuals to assess the situation which shows significant structural damage to the interior of the building.”

Council environmental health officers have been testing for asbestos and there is currently no evidence of fibres in the area.

If you have any information that may assist police, please call 105 or report online via https://www.police.govt.nz/use-105 using update report, with the reference file number 231015/6874.

People can also report any information anonymously via Crime Stoppers on 0800 555 111.