Tanard Jackson (34) during training camp drills, with Brandon Meriweather (left) and DeAngelo Hall (center) Aug. 1 (John McDonnell/The Washington Post)

Washington Redskins safety Tanard Jackson has been suspended indefinitely for violating the NFL’s substance abuse policy, two people with knowledge of the situation said Friday afternoon.

The Redskins had been waiting for word of the ruling on Jackson’s penalty, and appeared to keep six safeties as they rounded out their 53-man roster with the NFL’s 9 p.m. deadline for final cuts approaching. Now they are left with five after Jackson’s latest run-in with the league.

While a member of the Tampa Bay Buccaneers in 2010, Jackson was suspended indefinitely for violating the substance abuse policy and missed all but two games that year and six games in 2011 as well. In 2009 he was suspended and missed four games. In all, Jackson has missed 20 games in the last two seasons because of drug use.

The NFL confirmed Jackson’s suspension, issuing a written statement saying that Jackson had been suspended indefinitely without pay for a violation of the substance abuse policy. According to the league’s statement, Jackson’s suspension begins immediately and he is eligible for reinstatement beginning on Aug. 31, 2013.

It wasn’t immediately clear when Jackson failed the drug test that earned him his latest suspension, which was first reported by Fox Sports’ Jay Glazer. Under league rules, a third suspension puts Jackson at risk of banishment from the NFL. His case will be reviewed a year from now.

The Redskins currently have Brandon Meriweather and Madieu Williams slotted as their starting strong and free safeties. Jackson was competing for playing time at both positions. With Meriweather sidelined in Game 3 of the preseason, Jackson got the start.

Jackson missed Monday’s practice for what coach Mike Shanahan described as “personal” reasons, but Shanahan refused to elaborate. Jackson — like many veterans — didn’t play in Wednesday’s preseason finale.

The Redskins’ 53-man roster for now features Meriweather, Williams, Reed Doughty, DeJon Gomes and rookie Jordan Bernstine as the safeties. The team has four cornerbacks: starters DeAngelo Hall and Josh Wilson, and backups Cedric Griffin and rookie Richard Crawford.