Lasers are being used to monitor movement in Sydney’s cracked Mascot Towers and drones will soon film the building’s facade, as some shops in the complex reopen.

What caused the 10-year-old building to develop cracks in the primary support structure and facade masonry remains unclear.

Residents of the complex’s 132 units have been forced to stay elsewhere after the building was evacuated on June 14.

“Engineers are continuing to investigate the cause of the building movement,” residents were told in a written update on Friday.

The main focus was on earth movement and the water table.

Engineers were monitoring the groundwater for “potential geotechnical causes of building movement” and investigating ways of securing the building’s foundation slab, the update said.

Crack gauges are recording the extent of the damage, laser stations are monitoring movement and drones will soon be deployed.

“A close examination of (the) external facade via drone will be conducted over the following weeks,” the update said.

The IGA supermarket on the bottom floor of the building was expected to re-open for business on Monday.

Fair Trading is currently processing reimbursements of temporary accommodation expenses for residents.

-AAP