New Jersey’s largest school district began voluntary blood tests to check students for the presence of lead Thursday, a week after officials announced that elevated levels had been found in the drinking water.

The first testing concentrated on the Newark school district’s youngest students and began at the early childhood center, which was among 30 schools that had elevated lead levels in their water. About 67 families had registered for testing, said schools spokeswoman Dreena Whitfield.

As many as 17,000 children will be checked for lead poisoning, and the district will unveil a plan for wider testing next week, Whitfield said. The district said it plans to begin testing every tap at every school, including charter schools, in consultation with the EPA starting Saturday
Lead is known to severely affect a child’s development.

“Well, I just hope they can fix it, ’cause she has to go school here,” said Dionne Bradshaw, a Newark mother whose 4-year-old daughter was tested. “And if it can’t be fixed I will just have to put here in another school or home school her. Whatever is best for my daughter.”

Officials urged calm and said they don’t believe there are any serious health risks. They say the lead levels in some of Newark’s schools don’t compare to the crisis that has plagued Flint, Michigan.

WNYC in New York reported that the U.S. Environmental Protection Agency worked with Newark schools in 2003 after elevated lead levels were found.

The schools superintendent at the time, Marion Bolden, said they replaced the water fountains in almost every school, installed lead filters and sent letters home to parents.

“I think we were on top of it,” Bolden said. “We were aware that we had issues with the water. But there were protocols for air quality tests and water quality tests that we had to do.”

But according to workers, the protocols did not always get enforced. Gail Muhammad, who worked in Newark Public Schools from 1984 to 2014 she said she was never told to let faucets run in the morning to reduce lead.

“If we had to do chicken that day and we had to use the water, we turned the water on, put the chicken in the sink and start cleaning it,” she told WNYC. “And the manager at times would be sitting there and she never said, ‘Miss Muhammad you need to stop. You need to turn that water on and let it run for a few minutes.’ No our manager never enforced it.”

Lead hasn’t been found in the city’s water supply. It likely leached into the schools’ water through lead pipes or other building fixtures made of lead or lead solder.

F. Nana Ofosu-Amaah, executive director of the Newark schools’ office of early childhood, said not all the 67 families had their kids tested on Thursday. “Some of them started to call their pediatricians, and say ‘You know I’ll just wait and go to the pediatrician,'” she said.

Republican Gov. Chris Christie said Tuesday that his administration would work closely with Newark officials to help remedy the problem. “I want to make sure everyone understands this is a situation we’re concerned about, but it is not a crisis,” Christie said. “But we don’t want to let it become a crisis. So we’re on top of it.”