Washington. The FBI is joining a US criminal investigation into Flint, Michigan's water contamination crisis, a spokeswoman for the US Attorney's Office in Detroit said on Tuesday.

Gina Balaya, a spokeswoman for the US Attorney's Office in Detroit, said in an email that federal prosecutors in Michigan are "working with a multi-agency investigation team on the Flint water contamination matter, including the FBI, the US Postal Inspection Service, the EPA's Office of Inspector General ... and the EPA's Criminal Investigation Division."

A Federal Bureau of Investigation spokeswoman said the agency was determining if any federal laws were broken but declined further comment.

The city was under the control of a state-appointed emergency manager when it switched its source of tap water from Detroit's system to the Flint River in April 2014.

The more corrosive water from the river leached more lead from the city pipes than Detroit water did.

Dave Murray, a spokesman for Michigan Governor Rick Snyder, said the office "will cooperate fully with any authorities looking at what happened in Flint with the water. It's important to look at missteps at all three levels of government - local, state and federal - so such a crisis doesn't occur again."

Snyder has repeatedly apologized for the state's poor handling of the matter. Last week, he signed into law legislation approving $28 million to ease the crisis and extended a state of emergency in Flint until April 14.

Last week, Michigan Attorney General Bill Schuette named a special prosecutor and investigator to look into possible crimes stemming from the matter.

The Flint water scandal has garnered international attention in recent weeks. On Saturday, Democratic presidential candidate Hillary Clinton called for holding a primary debate in Flint.

In Washington, the Senate was expected to vote as soon as Tuesday afternoon on an energy bill amendment sponsored by Michigan Democratic Senators Gary Peters and Debbie Stabenow providing $600 million to Flint to help replace pipes and provide health care. The measure, which needs 60 votes in the Republican-led, 100-member chamber to pass, faces an uphill battle.

The US House Oversight and Government Reform Committee will hold a hearing on the Flint crisis on Wednesday and has invited the Environmental Protection Agency's acting deputy assistant administrator in its Office of Water to testify, along with an EPA researcher who raised concerns early about lead in the water.

Also testifying is Keith Creagh, the new director of the Michigan Department of Environmental Quality (DEQ). The previous director resigned in December in the wake of a critical report about the water.

The committee also called Darnell Earley, the former Flint emergency manager, to testify. The Detroit Free Press reported he may decline to testify.

Snyder's office said Tuesday that Earley, who is currently Detroit Public Schools emergency manager, will step down from that position on Feb. 29.

The EPA said in January that Susan Hedman, the head of its Midwest region was resigning, effective Feb. 1, over the water contamination crisis in Flint.

Hedman had played down a memo by an EPA employee that said tests showed high levels of lead in the city's water, telling Flint and Michigan administrators it was only a draft report.

Dan Wyant, the head of the state DEQ, resigned in December.

Residents complained of various health problems from using the local water after the switch, despite assurances from officials that the water was safe.

Flint, about 60 miles (100 km) northwest of Detroit, returned to using that city's water in October after tests found elevated levels of lead in the river water and in the blood of some children.

Reuters