A since amalgamated south Sydney council is being investigated over defects in an apartment building, as the owners of units they have been unable to live in for almost three years seek extended accommodation support.

Residents in the 132-unit Mascot Towers block on Bourke Street at Mascot were evacuated in June 2019 when cracks were found in supporting structure and masonry at the development.

The unit block’s owners’ corporation will have their accommodation support payment extended for another year if they lodge the documents to dissolve the strata scheme.

The NSW government announced on Thursday it will also investigate the former City of Botany Bay council in relation to the towers.

Local Government Minister Wendy Tuckerman said the investigation would seek to prevent a repeat of the incident.

However, the investigation is already facing hurdles.

“We are advised relevant council documents from that period cannot be located and may be missing,” Ms Tuckerman said.

“We are determined to gather as much information as possible on the issues that led to the defects in Mascot Towers.”

Botany Bay Council merged with Rockdale Council to form Bayside Council in 2016.

Mascot Towers was completed in 2009.

Unit owners will have their accommodation assistance package extended for another year if they lodge the Supreme Court documents to terminate their strata scheme.

Fair Trading Minister Eleni Petinos said the Mascot Towers Owners Corporation would lodge the documents imminently.

“Given this undertaking, the government is going to extend the accommodation funding support for a seventh time,” Ms Petinos said.

The lodging of documents with the court has been requested before support was extended in the past.

If extended, support for unit owners will run until the end of June 2023.

It came after owners visited NSW Parliament last month to deliver letters to Ms Petinos and Premier Dominic Perrottet asking for rental subsidies to be extended.

Opposition Better Regulation spokeswoman Courtney Houssos said the offer to extend support was five months overdue.

“The Mascot Towers owners have been forced to campaign for months for support they were already promised,” she said.

“This has caused them even more stress and heartache.”

Ms Petinos became Fair Trading Minister in December and was questioned over the Mascot Towers support at budget estimates in March.

In April last year the owners corporation was faced with a choice between selling the building at a massive loss for developers to demolish and rebuild on the site, or pay tens of millions to repair the building.

-AAP