The developer of a new high-rise apartment block in Sydney's west, which was evacuated after residents heard cracking noises on Christmas Eve, says there is "absolutely no danger for residents" and the company is confident the "localised" damage to an internal wall can be fixed.

About 300 residents were told to leave Opal Tower at Sydney Olympic Park on Monday afternoon after fine cracks and a split in the wall on level 10 sparked initial fears the building could collapse.

Most residents were allowed to re-enter later that evening, although 51 apartments in the 36-storey tower were deemed unsafe.

Some residents were still unable to get back into their apartments on Boxing Day.