FLINT — Five months after Flint changed its water supply due to problems with lead contamination and discolored drinking water, nearly 9 percent of the city’s sites tested for lead in the water continue to exceed federally acceptable limits, the governor’s office said on Tuesday.

Of 423 sites tested recently, lead concentration in the water at 37 sites exceeded the federal government’s action level of 15 parts per billion. Of those, eight sites had lead readings above 100 parts per billion, according to a statement from Governor Snyder’s office.

Flint’s water contamination and officials’ months-long delay in addressing the problem has sparked outrage and drawn attention from presidential candidates. Activists have demanded that Snyder resign. The governor is scheduled to testify before a congressional committee on March 17.

Homes with unacceptable lead levels will get an official visit and state support, including inspection of plumbing lines, bottled water, filters, blood testing and health information, the statement said. 

Regular testing will continue at approximately 600 sites across the city, the statement said.

Flint, a predominantly African-American city of 100,000 about 60 miles (100 km) northwest of Detroit, was under the control of a state-appointed emergency manager when it switched the source of its tap water from Detroit’s system to the Flint River in April 2014.

The more corrosive water from the Flint River leached more lead from the city pipes than Detroit’s water. Lead is a toxic agent that can damage the nervous system.

The city switched back to Detroit water last October after tests found high levels of lead in blood samples taken from children. 

Experts say it could take some time for anticorrosive chemicals now being added to the water to re-coat lead pipes so that they will not leach lead into the water.