A man has been arrested over last week’s train derailment in the NSW Illawarra which left four people injured.

The South Coast line commuter train slammed into a van that had been abandoned on the tracks before dawn at Kembla Grange last Wednesday.

The driver was trapped when the front carriage sheared off the tracks and landed in a nearby paddock and the remainder of the train rolled onto its side.

The 13 occupants of the train were freed, with four people taken to hospital for treatment of minor injuries.

A man was seen running from the tracks shortly before the fast-moving train hit the van, and police began a criminal investigation into the incident.

Police found a go-kart on a trolley in the rail corridor and a large hole in the security fence between the rail corridor and the raceway.

Inquiries revealed the van had been stolen earlier that morning from a nearby home.

Lake Illawarra detectives arrested a 47-year-old Berkeley man at Dapto about 1.30pm on Wednesday.

He has been taken to Lake Illawarra Police Station and is expected to be charged.