Team GB's Perri Shakes-Drayton will have to wait to see if she qualified for the final of the women's 400m hurdles.
Having got out of the blocks well, 23-year-old Shakes-Drayton gave herself every chance of finishing in the top two of her race.
However, she could only manage to finish third in a time of 55.19s.
She must now wait to see if she has made the final as a fastest loser.
Lashinda Demus won the race, while Kaliese Spencer came second.
