"There could be many more," Gov. Rick Snyder told CNN, "and we're assuming that."
One difficulty officials are facing, Snyder said, is that lead might no longer show up in a blood test after time has passed.
"We need to establish the right medical protocols, the public health pieces, the educational process things, to watch these kids for years that didn't have higher blood levels in terms of a blood test," he said. "Because they could be affected."
It's unclear how long it will take to replace lead pipes in Flint and throughout the state, Snyder said.
"It's too soon to tell," he said, "because I can't tell you how many pipes and where they are. But as a practice now, we should be working on that, very clearly."
In the meantime, the state government is providing bottled water and water filters for residents.
"This is about continuing to take action," Snyder said at a news conference earlier Wednesday.
Still, officials could not give a timeline on when people would be able to turn on their taps. Snyder said work is being done to find lead service lines, to be followed by a cost calculation for replacing them.
The short-term goal is to recoat the pipes, he said.
Michael Moore calls for governor's arrest
Calls for Snyder's resignation have been growing as criticism mounts over the government's handling of the crisis.
Filmmaker and Flint native Michael Moore has been particularly vocal, saying the governor should be arrested for his role in the water crisis. A plan to save $15 million on Flint's water bills may now cost $1.5 billion to clean up, Moore said.
"He's known about this for some time. He's trying to PR this thing right now, he's trying to blame civil servants for causing this or whatever," Moore told CNN's "The Lead with Jake Tapper." "This is squarely in his lap."
And more importantly, Moore said, the governor hasn't done anything to remove lead pipes to make drinking water safe again.
"Flint doesn't need bottled water sent to them," Moore said. "We need those pipes replaced, and not a single pipe has been replaced since they discovered lead in the water."
Snyder has blamed the situation on incompetent bureaucrats, specifically citing "a handful of quote-unquote experts that were career civil servant people that made terrible decisions."
Already, Susan Hedman, the U.S. Environmental Protection Agency's regional administrator for Flint, has resigned.
State Attorney General Bill Schuette said he is appointing a former prosecutor and Detroit's former FBI chief to join the investigation of the water crisis, creating a "conflict wall" between the state's inquiry and the lawsuits targeting the state.
The state investigation aims to determine "whether any Michigan laws were violated in the process that created a major public health crisis for Flint residents."
Governor appoints expert committee
Snyder announced Wednesday that he had appointed 17 health and environmental experts to a committee tasked with finding a long-term solution to the water crisis.
It's the latest of a number of task forces and investigations into the causes of the pollution and how to make things right for Flint.
Among those appointed to the committee is Virginia Tech University professor Marc Edwards, the researcher who conducted numerous tests on Flint's water system and was the first to publicly identify high levels of lead.
But some groups aren't waiting for the findings of a committee. On Wednesday, a group of organizations filed a federal lawsuit accusing the Flint and Michigan governments of violating federal laws that regulate drinking water.
Flint's state of emergency -- declared at municipal and state levels -- began years ago when the city suffered a financial crisis. The state took over the city's budget and decided to temporarily switch Flint's water source from Lake Huron to the Flint River to save money. After the switch, residents complained their water had problems, and high levels of lead were found in the water supply.
The city switched back to the Lake Huron water supply in October, but the damage was already done to lead pipes.
The focus of the committee, the governor's office said, is to make recommendations about the health of residents exposed to lead and determine potential upgrades to infrastructure.
On the same day Snyder spoke about the committee, a coalition of activists and national groups, including the Natural Resources Defense Council and ACLU of Michigan, filed a federal lawsuit.
The lawsuit alleges that city and state officials have violated the federal Safe Drinking Water Act.
The suit calls for a federal court to order the city and state governments to carry out additional water testing and to replace all lead water pipes at no cost to Flint residents.