The coach of Ethiopia's Genzebe Dibaba - the women's 1,500 metres world record holder and the 2015 world athlete of the year, has been arrested in Spain on doping charges.
Jama Aden was arrested along with a Moroccan physiotherapist athletics world governing body the IAAF said.
The arrests come less than two months before the start of the Rio Olympics and follow months of investigations following a tip off from the Spanish Agency of Health and Sport (AEPSAD), Catalan police told Reuters.
"The arrest today of distance running coach Jama Aden follows a lengthy investigation by the IAAF which began in 2013, working in close cooperation with Interpol, the Spanish authorities, including the Spanish National Anti-Doping Agency, Spanish police and other organisations," the IAAF said in a statement.
"The IAAF will use all available resources and powers to protect clean athletes and the integrity of our sport. This includes targeting and investigating individuals and coaches who are intent on exploiting athletes and promoting the use of prohibited substances."
Spanish police said the two men were held on suspicion of administering illegal substances to athletes.
IAAF officials also carried out doping tests on 27 athletes training in Sabadell, 20 km north of Barcelona, police said.
Dibaba, 25, the sister of triple Olympic distance champion Tirunesh Dibaba and Olympic silver medallist Ejegayehu Dibaba, is hot favourite for the 1,500m at the Rio Olympics.
In July last year in Monaco she ran a world record time of three minutes 50:07 seconds in the 1,500 metres to overhaul the 1993 mark of 3.50.46 set by China's Qu Yunxia.