The 19-year-old man remains in Tomaree Hospital on Sunday after suffering a medical episode at Nelson Bay Police Station during his arrest.

The man is alleged to have crashed a ute into a unit complex in Shoal Bay Road, causing severe structural damage to the building, on Saturday afternoon.

About 5pm police received reports that a Toyota Hilux had collided with the exterior wall of a unit complex along Shoal Bay Road.

Police said when nearby residents heard the crash and went to investigate, the driver allegedly reversed into a load-bearing wall of the same unit complex, causing part of the wall to collapse.

Residents of the unit complex managed to self-evacuate without injury or incident.

The vehicle was then seen driving away from the scene along Shoal Bay Road.

Police later received further reports that the same vehicle had crashed into a timber fence in Mistral Close, Nelson Bay.

Officers attended the location and found a 19-year-old man in the driver's seat of the vehicle.

The man was subjected to a breath test, which allegedly returned a positive reading.

He was arrested and taken to Nelson Bay Police Station for the purpose of a breath analysis.

While in the police station, the man suffered a medical episode, which required treatment by ambulance officers.

He was taken to Tomaree Hospital for non life-threatening injuries.

As part of the investigation, officers will await the results of a blood sample before taking any formal action against the man, NSW Police said.

Fire and Rescue NSW have assessed the damage to the Shoal Bay unit wall and have determined that a structural engineer will be needed to conduct a further examination of the wall.

Inquiries are continuing.