Specialist investigators are picking through shards of glass and twisted metal to work out why a gas bottle exploded in downtown Invercargill today, seriously injuring the occupant of a ute.

It's believed that a gas bottle being transported on the back of a ute exploded while travelling through an industrial part of Clyde St shortly before 3pm.

It blew the back off the ute, while blasting out the windows of another ute as well as several shop windows.

One person, a man aged about 40, was rushed to hospital with serious head and torso injuries.


Another person was treated at the scene for minor injuries.

"We had a report of a large explosion near a construction site just before 3pm,'' said Murray Hurst, police southern communications shift inspector.

Firefighters were on the scene within minutes.

"There was an explosion of a type of gas bottle,'' said Fire Service southern communications shift manager Riwai Grace.

Police evacuated the area and set up a 200-metre cordon.

Firefighters, helped by specialists from local gas companies, checked the scene and ensured it was safe before everybody was stood down.

Gas specialists and fire safety investigators are looking into the cause of the explosion. The type of gas bottle involved had not been released by officials, Mr Grace said. The Ministry of Business, Innovation and Employment (MBIE) has been informed.

Less than 15 minutes after the blast, just a few blocks away, emergency services were called to a serious car crash.

Two women, a 40-year and a 20-year-old, were trapped in the car and needed to be cut out before being taken to hospital with minor to moderate injuries.