Baylor coach Art Briles said in a statement that Chafin "has been suspended until further information is gathered."
According to the Tillman County Sheriff Facebook page, Chafin's vehicle was stopped for suspected speeding on Friday morning. During the stop, marijuana and marijuana candy, which had been purchased in Colorado, was discovered in the vehicle. Chafin was arrested and booked into the Tillman County Jail on possession of marijuana charges.
Tillman County is in southwest Oklahoma and just northwest of Wichita Falls, Texas.
Chafin has played a backup role in Baylor's backfield for the past three seasons, rushing 121 times for 578 yards and nine touchdowns as a junior in 2015.
Baylor University is currently on spring break.