Former Mayor, Dayne Walling, and former emergency manager Darnell Earley who was appointed by Michigan Governor, Rick Snyder, blamed the state and federals for high lead levels in the city's water on Monday.
Walling and Earley along with witnesses will testify at the two days of hearing by US House of Representatives Oversight and Government Reform Committee.
The water crisis caused a huge reaction with the public and led Michigan Governor, Rick Snyder, to heavy criticism. The governor repeatedly apologised for the state's poor handling of the crisis and scheduled to testify on Thursday.
The switch of Flint's water supply from Detroit to the Flint River in April 2014, made in a cost-cutting move, was made while Earley was the city's emergency manager.
The city switched back to the Detroit water system last October - after Earley had left the position as emergency manager - but the river's corrosive water leached lead from city pipes, causing a serious public health threat.
Early will appear on in front of the House committee on Tuesday
"Unthinkable errors all underscore that Flint’s crisis resulted from improper treatment of the water, an issue which fell squarely in the bailiwick of [the Michigan Department of Environmental Quality] and EPA," Earley said in the testimony released by the committee.
"We relied on the experts to verify that the water would not pose any threat to the community - the experts failed all of us," he added, citing state environmental officials and the US Environmental Protection Agency.
"I now wish that I had been more probative in my approach in delving deeper into the explanations I was receiving about what was being done," he said.
The EPA's former regional director, Susan Hedman will also be among those testifying on Tuesday.