The new 36-storey tower at Sydney Olympic Park had promised residents and investors sweeping views towards the city and hundreds of slick apartments characterised by "uncompromised quality".

The damaged panel at the centre of the investigation cracked plaster and jammed doors inside the unit block on Christmas Eve and there are fears over 16 more panels in the building.

The evacuations, just months after the building opened in August, left residents in limbo and stoked widespread unease about apartment defects amid the city's development boom.

NSW director of the builder, Icon, Julian Doyle said the urgent investigations would probe "cracking at a pre-cast [concrete] panel at a transfer in the building at level 10".

"We want to continue to investigate that same detail that replicates itself in about 16 locations throughout the building.”

Opposition Leader Michael Daley on Friday said residents at the tower were "shell-shocked" after being told they had to leave the building indefinitely as a precaution. He took aim at Ms Berejiklian, criticising the building debacle as "failure of leadership".

"This is not good enough," he said. “Days after the initial incident appeared, there are more questions to answer than there were when it first started."

But a spokeswoman for Ms Berejiklian said: “The Premier is upset that residents have been inconvenienced in this way, especially over Christmas and the New Year.

"She has been following the issue very closely and expects that the full weight of the law will be applied if anyone is found to have done the wrong thing. Safety can never be compromised.”

Speculation and recriminations flowed as hundreds of frustrated residents fled the 392-unit block for the second time since the crack appeared on Christmas Eve to allow for urgent investigations.

The incident also created a political headache for the NSW government in the lead-up to the next election, as it remains torn between a desire to increase housing supply across the city and community concerns about over-development.

Labor's planning spokeswoman Tania Mihailuk said the government "needs to understand that there are potential ramifications across the entire sector for all new high-rise developments and public confidence will need to be repaired promptly".

“Given the [planning] minister in September 2017 has approved an increase from 6000 to 10,700 units, and 14,000 residents to 23,500, at Sydney Olympic Park there is even more need to ensure that this investigation is comprehensive.

"There are so many new high-rise developments that have been approved and residents need peace of mind.”

Planning Minister Anthony Roberts appointed two engineering professors to investigate what caused the split to the six-by-three-metre pre-cast concrete panel on level 10 of the building.

"The government is confident in its planning and approval regime, which has been reformed greatly since the years Labor was in power," a spokesman for Mr Roberts said.

"We are awaiting the outcome of an investigation to conclude why exactly this fault occurred, and we will comment on the investigators' report at that time."

The tower, which sits on Sydney Olympic Park Authority land deemed "state significant", was approved by former planning minister Rob Stokes' department as a major development in June 2015.

A Planning Department spokesman this week said the state significant development process "follows the same rigorous and thorough assessment steps that would be applied if a development was being considered by council".

Sydney consultant Ross Taylor, who specialises in building facade and waterproofing defects, said this week that the building damage pointed to "a broader pattern in the industry".

He said the city's development boom in part meant that designers faced increased pressure from builders and developers to produce buildings that were cheaper and quicker to construct.

"Major defects are usually related to design rather than construction error," he said.

Builders Collective of Australia national president Phil Dwyer said the building defect was "the tip of the iceberg" and exposed wider problems within the building industry.

"We’ve had enormous failures everywhere," he said. "The dilapidation in the [building] industry over the past 10-15 years has been enormous."

Tenants Union NSW senior policy officer Leo Patterson Ross said a lot of new buildings came with defects – "not all of them are at this level" – and renters were being hit harder than owner-occupiers.

"It seems like over the past 10 to 15 years it appears to have gotten worse. The building standards have generally gotten better but also the types of buildings are changing."

But Bassam Aflak, the director of the building's developer Ecove, rejected the suggestions the damage signalled industry-wide problems and said there had been "no cutting of corners".

"It’s too early to leap to any conclusions, for instance, to speculate on wider building issues because of what appears to be one failed panel," he said.

University of NSW engineering expert Mark Hoffman, who will help lead the state government's probe into the incident, said suggestions of a crisis across the building industry were "very alarmist".

"The size of the cracks we’ve seen is quite large and that’s probably why everyone is treating this very carefully."