A massive plume of smoke over southeast Santa Rosa late Wednesday afternoon was part of a firing operation to slow the spread of a fire threatening Bennett Valley, said Bennett Valley Battalion Chief Darren DeCarli.

The operation was done above Annadel Heights. Firefighters have been working in the area all day attempting to get a solid containment line on that section of fire.

The plume of smoke rose over southeast Santa Rosa just before 5 p.m.

A large area of Trione-Annadel State Park’s 5,000 acres already has burned from the Nun fire since Sunday.