Invercargill Police are probing a suspected arson that's destroyed four Treetech vehicles

Emergency services were called to Queens Park after midnight yesterday, where arborists were restoring damage from October's storm.

Treetech CEO Chris Walsh says the fire caused about a million dollars in damage.

He says the company is committed to the recovery work, but opening Coronation Drive by Christmas may no longer be possible.

Police want anyone who saw anything unusual in the area Tuesday night or early Wednesday morning to come forward.