Random drug testing will be conducted on...

Random drug testing will be conducted on competitors at this year’s Boston Marathon, the Boston Athletic Assn. announced.

Under the plan, the first three finishers in the men’s and women’s competition, along with two additional runners in the top 25 from each race, are to be tested for drugs included on a list of banned substances compiled by the International Amateur Athletic Federation.

“The addition of prize money to the Boston Marathon has presented the new responsibilities of insuring legitimate times, and fair distribution of funds to athletes that earn prize money honestly,” BAA administrator Guy Morse said. “Drug testing is a logical and positive step in this direction.

Meanwhile it was announced that former world record-holder Rob deCastella of Australia will return to defend his title in the 91st marathon on April 20.