An Alameda County Coroner's office official confirmed to NFL.com Howard was one of two people killed in the early Monday crash.
Witnesses told police Howard's gray BMW sedan was speeding north along Interstate 880 at more than 100 mph when he lost control of the vehicle and clipped the rear of a truck, KRON-TV, San Francisco, reported.
After the impact, Howard's vehicle jumped the median into the freeway's southbound lane, where it collided with two other cars.
Howard played five seasons for the Raiders after being drafted by the club in 2006. His best season came in 2007 when he recorded 95 tackles, one sack and six interceptions, returning two of them for touchdowns.
He later played two seasons for the Cincinnati Bengals.
Howard was signed by Atlanta Oct. 22 and appeared in two games with the Falcons before being cut last week.
He compiled 492 tackles, six sacks and seven interceptions in 95 NFL games.