The wildfires ravaging Northern California could affect Sunday's scheduled NFL game between the Oakland Raiders and Los Angeles Chargers.

"We continue to monitor air quality conditions in the Bay Area and are in close communication with both the Raiders and Chargers, as well as local authorities," NFL spokesman Michael Signora said on Thursday. "At this point, the game remains scheduled for Sunday in Oakland."

At least 27 people have died in blazes that have burned 191,437 acres (77,500 hectares), and gusting winds on Thursday were hampering fire-fighting efforts.

A pall of smoke has reached south to Oakland, where the Raiders cut their training short for a second straight day on Thursday because of poor air quality. Some players wore masks under their helmets as they practiced.

The Raiders hold their pre-season training camp in Napa, north of Oakland, one of the areas hit by fire.

"My heart really goes out to the families," Oakland quarterback Derek Carr said. "When something like that happens and then someone tells you what it really is, you just sit there and think you're fortunate, you're blessed.

"Our thoughts and prayers are with all the families that have lost houses, loved ones. That kind of stuff, that's real life. That's hard."