All five players -- center Rodney Hudson, guards Gabe Jackson and Denzelle Good, tackle Kolton Miller and Abram -- were deemed high-risk contacts Thursday, sources told ESPN, confirming an NFL Network report.
All missed their second consecutive day of practice Thursday while in quarantine.
The Raiders had no new COVID-19 positive tests as of Friday morning, sources told ESPN.
Brown wasn't wearing Kinexon proximity device at all times in the facility and there were instances of the offensive linemen unmasked together on the sideline during practice while the team was in intensive protocols, a source told ESPN's Dianna Russini on Friday.
With Brown and the other four starters on the reserve/COVID-19 list, the Raiders have just five remaining offensive linemen on their 53-man active roster, along with two practice-squad offensive linemen.
NFL rules stipulate that teams must have at least eight offensive linemen on their 48-man rosters for game day. If the Raiders are unable to dress at least eight offensive linemen for Sunday's game, they would be allowed a maximum of only 47 active players.
Abram and the offensive linemen must quarantine for five days plus their last day of contact, which was Monday -- which means they conceivably could be cleared Sunday morning via a point of care (POC) test.
The NFL announced Thursday that the Raiders' game against Tampa Bay -- originally scheduled for Sunday night -- had been moved to 4:05 p.m. ET "out of an abundance of caution to ensure that a game would be available for fans on Sunday Night Football."