The photo posted on Bess' Twitter account shows a substance that appears to be marijuana. The tweet has since been deleted.
"The team is aware of the photos and looking further into the situation and will deal with the matter internally,'' a team spokesman said in a statement.
Bess, 28, had 42 catches for 362 yards and two touchdowns but led the NFL with 14 drops. He is scheduled to make $3.067 million in 2014 after making $2.68 million last season.