Athletics global governing body is to launch a doping crackdown on elite marathon runners after scandals involving top Kenyan and Russian stars.
Organisers of the top races in London, New York, Boston, Chicago, Tokyo and Berlin have agreed to finance extra testing of top runners by the International Association of Athletics Federations (IAAF).
The finance from World Marathon Majors (WMM) means that the top 150 runners will face tougher testing after races and out of competition.
Failed tests by Russia's Liliya Shobukhova, who was the second-fastest women in history, and Kenya's Rita Jeptoo, three-time winner of the Boston marathon, sullied the name of one of the original Olympic disciplines.
Jeptoo — who in the past two years has achieved the Chicago/Boston double — was one of 35 Kenyan athletes suspended over the past two years for taking banned drugs.
The WMM "offered their contribution to our programme," said Thomas Capdevielle, the IAAF's anti-doping manager, announcing the clampdown.
He said it "basically means systematic ABP (athletes biological passport) testing at the races on all the elite field, as we have been doing for the past two years, but also urine tests out of competition."
Drug investigators would have "more resources to follow a group of 100-250 elite marathon runners in the world," Capdevielle added.
"So we will have like a sub-group that we will very closely follow up."
He added that a new drug testing laboratory to be opened in Kenya within three months would be a "significant achievement."
Capdevielle called it a "priority project" that would analyse blood tests on Kenyan, Ethiopian, and Ugandan athletes.
Shobukhova was banned for two years in April, 2014 over suspicious blood values in her biological passport. Her three wins at the Chicago marathon and one at the London race were all annulled.
The suspension was backdated by the Russian federation to January 2013 and Shobukhova theoretically became free to run again last month.
Capdevielle said marathon runners are harder to monitor for drugs as they compete less often.
But the IAAF had long been suspicious of Shobukhova's performances. The Russian won three Chicago marathons in a row up to 2011 and the London version in 2010.
"When we started the passport in 2009 she was on our list of go-after athletes, definitely," the IAAF told a press briefing.
"It was typical data probably suggesting a doping pattern. Yes she was suspicious," he added.
"There was not only this data, there was other information on Shobukhova. We do not only focus on blood data, we focus on the rise in performance," said Capdevielle.
"We work a bit like the police — intelligence and eyeing this information and trying to use it in the best possible way — and that is why her and other athletes were already on our target list when we started the passport on day 1."
Capdevielle said that 42 athletes have now been caught and sanctioned because of biological passport faults. More than half of them are Russian.