The truck driver suffered moderate to minor injuries.
Thomas's employer declined to comment, but Greg Lazzaro, general manager of safety, health and environment at Waka Kotahi NZ Transport Agency said the company was saddened by Thomas's death.
"Our thoughts are with all of those affected by this tragic event.
"Everyone should be able to go to work and expect to come home safely at the end of the day," he said.
The police serious crash unit and WorkSafe were investigating and they would receive their reports once completed.
Until then, Lazzaro said he was unable to make any further comment.
Earlier, a St John spokeswoman said two ambulances and a helicopter were sent to the scene.
A cafe owner in the area said she had seen a lot of emergency service vehicles driving past before closing the road.
"There were about four police cars, a helicopter, two ambulances," she said.
