Cullen Jones, Cesar Cielo come join first in 50m freestyle semi-final

The first of tonight's swimming action resulted in the United States' Cullen Jones and Brazil's Cesar Cielo finishing joint top in the first heat of the 50m freestyle semi-final.

The pair reached the end of the pool in 21.54s, while the second heat saw another Brazilian, Bruno Fratus, reach the quickest time 21.63s.

Anton Ervin for the USA clinched a time of 21.62s in the first heat with Trinidad and Tobego's George Bovell recording 21.77s.

Meanwhile, American hopeful Ryan Lochte is on course to claim a second gold medal in the 200m backstroke final.