Drug-row Brazilian Cesar Cielo was part of a three-way lead in the men\'s 50m freestyle heats as he pressed his bid for a second controversial gold medal at the Shanghai world championships. The reigning world and Olympic champion, who escaped a drugs ban on the eve of the competition, on Friday led timings alongside Nathan Adrian of the United States and Trinidad and Tobago\'s George Bovell, with all three clocking 22.03sec. \"I feel I couldn\'t have done better. I\'ve done good with a lot of inspiration and concentration,\" Cielo said. \"I\'m looking forward to a high speed tonight.\" Cielo was whistled by the crowd and given the thumbs-down by a fellow swimmer after winning the 50m butterfly on Monday, demonstrating disquiet at his all-clear to swim despite testing positive for a banned diuretic. Cielo, 24, who is also the world record-holder over 50m and 100m, denies wrongdoing and blames a contaminated caffeine supplement for his test results in May. Three of his Brazilian team-mates also tested positive for furosemide. In other results, Olympic champion Michael Phelps was fifth fastest in the 100m butterfly heats as he bids to resurrect his campaign after three surprise defeats. The 14-time Olympic gold-medallist was beaten in world record time by rival Ryan Lochte in the 200m individual medley late on Thursday, after also coming off second best to his team-mate in the 200m freestyle. Phelps, into the last year of his record-breaking career, was also part of the United States 4x100m freestyle relay team that lost its six-year grip on the world title, coming in third behind Australia and France. \"I\'m fine with my result today. I am looking forward to tonight\'s semi-finals. We\'ll always have ups and downs,\" Phelps said. Zimbabwean world record-holder Kirsty Coventry placed seventh in the 200m backstroke heats and admitted illness had given her a \"rough meet\" after she missed out on a place in the 200m individual medley final. \"It\'s been a bit of a rough meet,\" she said. \"I had flu two weeks before I got here which wasn\'t the best preparation. I\'m trying to have strategic races and hope that gets me into finals.\" Elsewhere Swedish world record-holder Therese Alshammar led timings in the women\'s 50m butterfly and 16-year-old American Missy Franklin, who already has three medals in Shanghai, was quickest in the 200m backstroke. British Olympic champion Rebecca Adlington was quickest in the women\'s 800m heats and the United States were fastest into the men\'s 4x200m freestyle semi-finals, ahead of Japan and France.