Newark will test 17,000 children for lead poisoning after elevated levels of the toxin were found in the drinking water at nearly half of the schools in New Jersey's biggest city.

Newark Mayor Ras Baraka at a news conference on Wednesday, March 9, 2016, in Newark, N.J. (AP Photo/Julio Cortez) reports that city Health Director Hanaa Hamdi told officials Tuesday that testing will start with some 2,000 toddlers who attend early childhood centers. Lead is known to severely affect a child's development.

In the week since the higher lead levels were first reported, officials have urged calm. They say the lead levels in some of Newark's schools don't compare to the crisis that has plagued Flint, Michigan.

It's unclear how long Newark's kids have been exposed to higher concentrations of lead. Schools are now using bottled water for drinking and cooking.