SAN FRANCISCO -- The string of Bay Area burn bans will continue Saturday for a sixth consecutive day, Bay Area Air Quality Management District officials announced Friday.

The Spare the Air Alert, the 21st since the season began Nov. 1, prohibits burning wood, manufactured fire logs or solid fuels either indoors or outdoors for 24 hours, including in fireplaces, wood stoves, pellets or fire pits.

First-time violators may be subject to a $100 fine or be given the option of taking a wood smoke awareness class. Subsequent violations will result in fines of $500 or more.

According to the district, the continued alerts are the result of a high-pressure system trapping fine particulate matter in the region, making air quality polluted and unhealthy.

The Winter Spare the Air season extends until Feb. 28.

Contact Jeremy Thomas at 925-847-2184. Follow him at Twitter.com/jet_bang.