Residents of a high-rise unit block in Sydney's south face are waking up with no idea of when they can return home after a crane collapsed on to the side of their building.

Authorities have begun investigating what caused the Sunday morning incident at Wolli Creek as engineers assess how to safely dismantle the crane, which smashed into a top-floor penthouse apartment of the at least 10-storey building, crushing the balcony.

It comes as a construction union calls for a halt to the use of Cantilever cranes until independent engineers’ reports can prove they have been put together correctly.

All 160 residents of the apartment complex on Brodie Spark Drive were evacuated when the crane, which firefighters estimate is about 30 metres tall, toppled on Sunday.

They could be forced to remain in temporary accommodation until at least Wednesday, with contractor Probuild estimating it could take another two to three days to safely dismantle the crane.