A pediatrician who raised concerns about elevated lead levels in children's blood in Flint, Michigan, says a new study provides the strongest evidence yet of a link between those levels and the cash-strapped city's water system.

In a report released Monday, Dr. Mona Hanna-Attisha of Hurley Children's Hospital and other experts said a more refined analysis shows that areas in Flint with the highest levels of lead in tap water corresponded with where children with the highest blood-lead levels lived.

Hanna-Attisha says the percentage of children with abnormally high levels more than doubled after the Flint River became the city's drinking water source. In some areas, the increase was even higher.

Flint stopped tapping Detroit's water system to save money in April 2014. The decision was reversed in October.