Fire crews have stayed overnight at the scene of a suspicious fire on Blenheim's Wither Hills.

The 7ha blaze started in pine trees south of the Rotary Lookout at 11.45am yesterday, the fire service said.

Helicopters using monsoon buckets helped contain the fire by 4pm.

Authorities were treating the blaze as suspicious, southern fire communications shifts manager Rachel Butler said.


"Police were called and they've had a crew on overnight, just keeping a watch."

The fire also forced the nearby Omaka Aviation Heritage Centre to close.

Museum staff member Kelsey McNabb said it was less than three kilometres from the museum and was at one point large enough to send black smoke over its large hangars.

Meanwhile, some ash fell on the Wither Hills winery.

A cafe staff member, Gemma, said she didn't believe the ash had had any adverse effect on the winery and the blaze was about 5km away.

Wither Hills Farm Park contains walking and mountain biking tracks and sheep. The tracks were closed until further notice.

Residents of houses which skirted the Wither Hills were asked to keep away from the scene, although no properties were under immediate threat.

Two boys were being spoken to about the fire by police, RadioLive reported.