A corporate box at a Nelson speedway was gutted by fire overnight.
Firefighters were called to the blaze at the Top of the South Speedway at 12.20am, Fire Service spokesman Andrew Norris said.
The fire was in narrow two-storey building alongside the raceway. The lower level contained shops and the upper level was a corporate box.
Mr Norris said the building was well ablaze when firefighters arrived.
Crews from Richmond and Stoke battled the blaze with water from two rural fire tankers.
Nobody was in the building and there was no one at the speedway at the time, Mr Norris said.
He did not know whether there had been an event at the speedway earlier in the evening.
The cause of the fire was yet to be determined and was being treated as suspicious.
A fire investigator was heading to the scene this morning.
The Nelson Speedway Association said on its website that the fire had "pretty much destroyed" the McCall Complex, which housed the speedway's corporate boxes, souvenir shop and food outlets.
"Although this is a major setback for the club and its patrons we will still be racing tonight and for the rest of the season which is great news. As they say in show business, 'The show must go on' and the only way for us to do that is to 'Do it in the dirt'."