A second person has been charged over a fire started on the side of a Tasman highway in February.
The incident occurred near the Moutere Highway on Wednesday, February 27, Detective Senior Sergeant Craig Johnston said.
A 24-year-old woman has since been charged with arson.
A 34-year-old man was earlier charged with arson on Wednesday, March 6, they said.
The highway fire caused extensive damage to a wide area of pine forest, resulting in the evacuation of local residents.
The pair have also been charged in relation to a fire on the side of the road in Pigeon Valley, near Wakefield, on Wednesday, March 6.
The investigation in relation to the Rabbit Island fire on Wednesday, February 6, and the Iwa Road fire, in Nelson, on Friday, February 8, are ongoing, Mr Johnson said.
Anyone with information has been urged to contact Nelson police on (03) 546 3840, or anonymously through Crimestoppers on 0800 555 111.