Police have released footage of the missing boy with his brother Eric from CCTV images captured on Monday evening.
The footage was captured at Waitarere Four Square.
Police plan to resume the search for Alex tomorrow morning.
Inspector Sarah Stewart said the public could help by reporting any sightings of Alex and his adult brother from Monday.
She said with each passing hour, police grew more worried for Alex.
Alex's family have released a statement.
"We would like to thank all those involved in the search for our son, brother and cherished family member."
"We appreciate the efforts and support from friends, family members and the public," the family added.
"At this time we request that our privacy is respected at this difficult time."
Earlier, a man connected to the disappearance of the missing boy appeared in court.
The charge names Forest Rd, Waitarere as the location of the alleged offence.
Forest Rd is where the search for Alex is centred.
The man, who is aged in his 20s, was granted interim name suppression and remanded in custody by consent until October 14.
The court heard he was likely to face at least one further, unspecified charge.
He appeared in the dock wearing a sack-like, prison-issue vest with three policemen flanking him.
He said nothing and kept his head down for much of his appearance.
The public gallery was almost deserted for his appearance this afternoon.