The 32-year-old tested positive for the banned substance EPO in a test by athletics governing body IAAF.
The 32-year-old tested positive for the banned substance EPO in a test by athletics governing body the IAAF.
Sumgong also won the 2016 London marathon and was due to defend her title later this month.
"We can confirm that an anti-doping rule violation case concerning Jemima Sumgong (Kenya) has commenced this week," the IAAF said in a statement.
The athlete tested positive for EPO (Erythropoietin) following a no-notice test conducted in Kenya.
This was part of an enhanced IAAF out-of-competition testing programme dedicated to elite marathon runners which is supported by the Abbott World Marathon Majors group.
If Sumgong's B sample is confirmed as positive and she is subsequently banned it will be a massive blow for Kenya. These news comes in the wake of a four-year ban handed to Kenya's multi-marathon champion Rita Jeptoo, Sumgong's former training partner, after she tested positive for EPO in 2014.
This is coming days after the IAAF claimed that its systems were hacked putting at risk its documents.
The latest cases will be seen by observers as evidence of how the IAAF is making progress in the region after previous official criticism of anti-doping regimes in Kenya and Ethiopia.
Both countries have in the past been deemed non-compliant with the World Anti-Doping Agency's (WADA) code.
Just the other day the athletics body in Kenya NOCK adopted the new constitution that was pushing for reforms in athletics.
The adoption will see Kenya hold election next month to inject new blood in the leadership of Nock.