Bond was set at $2,500 for Foster, who was a first-team All-American for the Alabama Crimson Tide in 2016 and also won the Butkus Award as the best linebacker in college.
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"The San Francisco 49ers organization is aware of the matter involving Reuben Foster and we are currently gathering all relevant facts," the team said in a statement.
Foster recorded a team second-best 72 tackles in 10 games during his rookie season after being selected with the 31st overall pick of the 2017 NFL Draft.
In order to draft Foster, the 49ers dealt their second-round pick (No. 34 overall) and a fourth-rounder acquired from the Chicago Bears earlier on draft night (No. 111 overall) to the Seattle Seahawks for pick No. 31.
Foster entered the draft after being sent home early from the NFL's annual scouting combine in Indianapolis after he got into an argument with a hospital worker and had a urine sample show up as diluted.
The 23-year-old Foster was the NFL's Defensive Rookie of the Month in November.