WASHINGTON -- Michigan should have required the city of Flint to treat its water for corrosion-causing elements after elevated lead levels were first discovered in the city's water a year ago, the state's top environmental regulator told Congress Wednesday.

State officials "relied on technical compliance (with the law) instead of assuring safe drinking water," said Keith Creagh, director of the Michigan Department of Environmental Quality. He called that a mistake.

The hearing was the first on Capitol Hill since the lead contamination crisis in Flint made national news last year, and frustrated Democrats complained that the Republican-led committee didn't ask the state's GOP governor to explain what happened.

Flint is under a public health emergency after its drinking water became tainted when the city switched from the Detroit system and began drawing from the Flint River in April 2014 to save money. The city was under state management at the time.

Water was not properly treated to keep lead from pipes from leaching into the supply. Some children's blood has tested positive for lead, a potent neurotoxin linked to learning disabilities, lower IQ and behavioural problems.

Michigan Gov. Rick Snyder has apologized repeatedly for the state's role in the crisis. Snyder and state legislators have enacted $28 million in emergency Flint funding for the current fiscal year. Snyder is expected to propose an additional $30 million in state funding to help Flint residents pay their water bills.

The crisis has taken on partisan overtones, as Democrats blame the Republican governor and some Republicans target the federal Environmental Protection Agency for failing to intervene sooner.

State officials are not the only ones who made mistakes in Flint, Creagh testified. All levels of government deserve blame in the Flint crisis, he says.

City officials did not follow proper protocol in conducting lead sampling of homes and the U.S. Environmental Protection Agency "did not display the sense of urgency that the situation demanded," Creagh told the House Oversight and Government Reform Committee.

"What happened in Flint was avoidable and never should have happened," said Joel Beauvais, acting chief of the EPA's water office.

EPA's regional staff urged Michigan officials "to address the lack of corrosion control, but was met with resistance," Beauvais said. State delays in responding to the lead crisis "and in informing the public of ongoing health risks raise very serious concerns," he said.

Rep. Brenda Lawrence, D-Mich., said government at all levels failed Flint in providing a basic need.

"We have also failed their most basic trust," Lawrence said. While Lawrence applauded Wednesday's hearing, she and other Democrat renewed their call for Snyder and other state officials to testify. The oversight panel's Republican majority did not call Snyder to testify Wednesday.

Creagh, in his testimony, focused on a June 2015 memo by an employee in EPA's Midwest regional office that outlined problems with Flint's water. The memo was not formally delivered to state environmental officials until November -- after the state had begun taking actions to address the lead problem, Creagh said.

"Legitimate concerns raised by EPA's own expert staff were not elevated or provided to either the city or the state for review and action until after the state's response was well underway," Creagh said.

While immediate treatment of the water was not required after lead was first discovered in January 2015, "corrosion treatment should have been required by the MDEQ," said Creagh, who took over as head of the state agency last month following the resignation of Dan Wyant.

Detroit schools emergency manager Darnell Earley, who was state-appointed emergency manager for Flint when its water source was switched, had been asked to testify at Wednesday's hearing but declined. The oversight committee issued a subpoena to Earley on Tuesday, but his lawyer refused service, a committee staffer said.

In the Senate, Democrats have proposed a $600 million package of federal aid for Flint, but face opposition from some Republicans who don't want to add to the federal deficit. Democrats hoped to include the package in a bipartisan energy bill.

Sen. Debbie Stabenow, D-Mich., said Wednesday she was negotiating on the issue and thought she had an agreement, but now faces resistance.

"We want this fixed," Stabenow said on the Senate floor. "We're not going to let procedural issues get in the way."