HORSHAM detectives believe a grass fire in a Horsham backyard was deliberately lit.
Horsham Crime Investigation Unit and Country Fire Authority experts examined a Fechler Avenue property on Wednesday.
Detective Senior Constable Brad McKenzie said the fire was believed to be suspicious, although the cause was yet to be determined.
"A 45-year-old woman from Horsham is assisting police with their inquiries," he said.
"We urge any witnesses or people with information to call Horsham CIU on 5382 9200, or Crime Stoppers on 1800 333 000."
About 35 square metres of dry grass in the backyard went up in smoke on Tuesday night.
Country Fire Authority District 17 operations officer Peter Bell said fire-fighters arrived at 9.14pm to find the fire had also crept under a fence and into a neighbouring property.
"It was quickly extinguished," he said.