Bears DE Gaines Adams died on Sunday morning in Greenwood, S.C., at 26.
Greenwood County coroner Jim Coursey told WYFF-TV that Adams was pronounced dead at Self Regional Hospital. He also told the station that Adams appeared to be in good health before his passing.
An autopsy was scheduled for Sunday.
Adams was the fourth overall selection in the 2007 draft by the Bucs. Bucs traded him to the Bears in October for a second-round draft pick in April.
He appeared in 15 games last season with the Bears and Bucs and recorded one sack.
Adams is the second NFL player to die in as many months, following the passing of former Bengals WR Chris Henry in December.
UPDATE: ESPN reported that the coroner ruled Adams died of cardiac arrest because of an enlarged heart.– Sean Leahy