Great Britain's Liam Phillips has missed out on a medal in the men's BMX after falling in the final, with Maris Strombergs of Latvia successfully defending his Olympic title.
The Latvian saw off the challenge of Australian Sam Willoughby and Carlos Mario Oquendo Zabala of Colombia, who take silver and bronze respectively.
Phillips started well and occupied second place in the early stages of the race, but was soon dragged back into the pack.
He was then caught in a collision with another rider, took a nasty fall and could not recover to finish the race.
Fellow Briton Shanaze Reade also failed to medal after finishing sixth in the women's final.