Russian track and field athletes were the most tested by the Russian Anti-Doping Agency (RUSADA) in the first half of this year, the organisation has claimed.
In its latest report, RUSADA said 675 track and field competitors had undergone doping tests in the first six months of 2019.
The document reveals Sergei Dubrovsky, the national 800 metres champion, is the most tested athlete.
RUSADA claim he has been subjected to nine tests in the period from January to June.
He is yet to be granted neutral status by the International Association of Athletics Federations (IAAF), which has allowed Russian athletes to compete at its events as long as they fulfil certain criteria while the Russian Athletics Federation (RusAF) remains suspended.
The figure for athletics is considerably larger than the next highest sport, with 221 tests conducted on weightlifters so far this year.
According to Russia's official state news agency TASS, doping samples of 143 swimmers, 122 cross-country skiers and 94 biathletes have also been collected by RUSADA.
RUSADA revealed earlier this month that it had uncovered 102 suspected anti-doping rule violations by Russian athletes in 2019.
The organisation also confirmed an investigation into 33 athletes who are facing anti-doping proceedings for using banned treatment from a doctor at a sports academy in Chuvashia.
A total of 19 these cases are from athletics, RUSADA said.
The IAAF extended the ban on the RusAF for the 11th time in June.
Banned coaches still being active and allegations of forged documents to help world indoor high jump champion Danil Lysenko avoid a suspension were the main reasons given by the IAAF for maintaining the RusAF's ban.
Russian President Vladimir Putin has ordered the Russian Olympic Committee to ensure that the IAAF ban is lifted in time for the Tokyo 2020 Olympics.