Darius Simpson, an Eastern Michigan University student from Akron, Ohio, carries water he brought to donate for Flint, Michigan, residents during a rally Jan. 24, 2016, at Flint City Hall. Brett Carlsen/Getty Images

The FBI said on Tuesday it was joining a criminal investigation of lead-contaminated drinking water in Flint, Michigan, exploring whether laws were broken in a crisis that has captured international attention.

Federal prosecutors in Michigan were working with an investigative team that included the FBI, the U.S. Postal Inspection Service, the U.S. Environmental Protection Agency's Office of Inspector General and the EPA's Criminal Investigation Division, a spokeswoman for the U.S. Attorney's Office in Detroit said.

An FBI spokeswoman said the agency was determining whether federal laws were broken, but declined to make any further comment.

EPA Administrator Gina McCarthy met with officials and community leaders in Flint and told reporters she could not give a timeline for fixing the problem. She said the agency was examining where it may have fallen short, but declined to address the criminal probes.

The city, 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.

Flint switched back last October after tests found high levels of lead in blood samples taken from children. The more corrosive water from the river leached more lead from the city pipes than Detroit water did. Lead is a toxic agent that can damage the nervous system.

Michigan Governor Rick Snyder, who extended a state of emergency in Flint until April 14, has repeatedly apologized for the state's poor handling of the matter.

The ability to seek criminal charges under U.S. environmental laws is limited, according to Peter Henning, a law professor at Wayne State University in Detroit and a former federal prosecutor. Prosecutors would need to find something egregious like a knowingly false statement.

"You need something that is false to build a case," he said.Simply failing to recognize the seriousness of the situation would not rise to that level, Henning added.

In Washington, Senators Gary Peters and Debbie Stabenow, Democrats from Michigan, pushed for $600 million in aid, mostly in federal funds, to help Flint replace pipes and provide healthcare.

Senator James Inhofe, an Oklahoma Republican who chairs an environmental committee, said an agreement to help Flint was close and would be a combination of revolving funds and other aid. Money from a revolving fund is like a loan, with the money going to the recipient and then being repaid so there is no net cost to U.S. taxpayers.

Senator John Cornyn of Texas, the second-ranking Republican in the Senate, said aid to Flint must not add to U.S. budget deficits for "what is a local and state problem."

U.S. Representative Candice Miller, a Michigan Republican, proposed an emergency bill to provide $1 billion in funds to be used to replace Flint's water pipes.

The U.S. House Oversight and Government Reform Committee will hold a hearing on Wednesday on the Flint crisis. The head of the Michigan Department of Environmental Quality, Keith Creagh, will apologize for its handling of the case, and an EPA water official will tell the committee that reforms must be enacted to prevent a repeat, according to advance testimony.

(Additional reporting by Ben Klayman in Detroit, Serena Maria Daniels in Flint, David Bailey in Minneapolis and Tim Gardner and Richard Cowan in Washington; editing by Jeffrey Benkoe, Grant McCool, G Crosse and Dan Grebler)