LONDON (AP) UEFA has dismissed the notion that drug use may be common among top footballers after a study it commissioned showed a high number of suspicious testosterone levels.

The study, which was published in a monthly science journal this month, said high testosterone levels were found in urine samples of 7.7 percent of the 879 players tested by researchers. Those levels could indicate the use of anabolic steroids.

UEFA never publicized the research, which came to light Sunday in a report by German broadcaster ARD, but announced this month that steroid use by players was being added to its biological passport program this season.

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''The study simply shows that the introduction of steroidal biological passport in football would be beneficial by offering further analysis possibilities in case of atypical test results,'' UEFA said. ''UEFA has had a very thorough anti-doping program for many years with over 2000 tests a year and only two occurrence of positive tests, both for recreational drugs, which proves that doping in football is extremely rare.''

The study was based on 4,195 urine samples taken mainly from players who featured in the Champions League between 2008 and 2013. The results were analyzed by scientists from 12 anti-doping laboratories in Europe.

UEFA said no ''B samples'' were taken and no additional analysis was undertaken to confirm whether the high levels of testosterone were due to doping or not.