He is currently in hospital.
Mitchell Piper, 27, lives and works at a neighbouring property and said the police arrived at the scene about 7.30am-8am.
"I heard the sirens this morning, they were pretty loud."
He said there was initially only one police car and policeman, who was talking to the construction workers and stayed for between two to three hours.
"He was in and out of his car and wandering around.
"I was wondering what was going on, but I couldn't see anything really."
A police spokeswoman at the scene said the man was found around the corner and out of sight from the road.
Construction work has now restarted at the site.
When approached by the Herald for comment, a construction site manager referred all questions to police and Auckland Council.
Neighbours say the construction work started months ago.
Other neighbours said they also heard police sirens this morning about 7.30am, but do not know what happened.
The police spokeswoman told the Herald that police are currently interviewing several witnesses.
These witnesses left the scene with police.
When asked about site security and how the man had entered the site, she said another update will be provided in a few hours and will address the circumstances of the incident.
Police were alerted by St John Ambulance this morning, the spokeswoman said.
A WorkSafe New Zealand spokesperson said they had been notified of the incident and are making some follow-up inquiries.