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…