Three state and local officials involved in Flint’s water contamination crisis were criminally charged on Wednesday for their roles in the two-year public health debacle, the first round of what’s expected to be many charges against government employees.

The officials are facing multiple felonies and misdemeanors accusing them of misconduct, tampering with evidence, and “willfully” misleading federal officials, more than six months after Governor Rick Snyder of Michigan admitted his administration gravely misunderstood the extent of a lead contamination problem in Flint.

“Our system of justice applies to everyone,” Michigan attorney general Bill Schuette said at a press conference announcing the charges. “It’s not rigged. No one is above the law. Not on my watch.”

He added: “We will hold each and every person – each and every person who breaks the law will be held accountable.” The attorney general said he would “guarantee” that more charges are forthcoming against individuals related to the debacle.

Schuette’s office accused Mike Glasgow, Flint’s laboratory and water quality supervisor, of willful neglect of office and tampering with evidence, saying he falsified documents that suggested Flint tested for lead in homes with lead service lines.

Mike Prysby, an official with the Michigan department of environmental quality; and Stephen Busch, who previously headed the environmental department’s office of drinking water; are charged with multiple counts of misconduct in office, conspiracy to tamper with evidence, tampering with evidence and safe drinking water act violations.

The charges carry possible sentences ranging from four to five years in prison each, or fines up to $10,000. The officials were not present in court on Wednesday when the warrants were issued, according to reports, and they have yet to be arraigned.

The charges stem from a criminal investigation launched in January by Schuette’s office, which created a team of roughly 20 full- and part-time investigators. Investigators have said the scope of potential criminal charges that could be considered include misconduct in office and involuntary manslaughter, and the inquiry continues.

According to a complaint issued on Wednesday, Busch and Prysby “willfully and knowingly” misled federal officials from the Environmental Protection Agency (EPA) and the Genesee County health department between February 2015 and November 2015. The misconduct in office charges, the complaint stated, mean officials violated their “duty to provide clean and safe drinking water” to residents in the county.

Flint resident Angela Hickmon, 56, chants during a protest outside city hall in January. Photograph: Jake May/AP

In addition, the complaint continued, Prysby authorized the Flint water treatment plant to come online in April 2014, despite knowing it was “deficient in its ability to provide clean and safe drinking water”. It was around that time that Glasgow, according to emails released in recent months, warned advisers that the water treatment plant wasn’t prepared to be fully operational.

Schuette’s office also accused the two environmental officials of Safe Drinking Water Act violations for failing to ensure Flint’s water was treated using optimized corrosion controls. As a result, Flint’s water became contaminated and corroded lead from the inside of water pipes before flowing into thousands of households across the city. Health officials documented a significant spike in cases of legionnaires’ disease in the area surrounding Flint, including 12 deaths, but officials haven’t concluded the water source was the cause of the increase. Officials still haven’t declared the water safe to drink.

Glasgow was charged with tampering with evidence for “knowingly and intentionally” altering lead and copper reports on three occasions between February and August 2015, according to the complaint. When an American Civil Liberties Union of Michigan reporter asked Glasgow about the tests last fall, he admitted it was nearly impossible to ensure tests were being conducted at homes with lead service lines.

“We throw out bottles everywhere just to collect as many as we can to try to hit our numbers,” he told the ACLU.

Attorneys for the charged officials couldn’t be immediately reached for comment. Schuette said no one has been granted immunity, but investigators didn’t rule out possible plea deals.

“The first person on the train gets the best seat,” said Andy Arena, the former chief of the local FBI office and chief investigator of the team.

Though the charges focused mostly on the city’s lead contamination, Flood said Busch and Prysby both impeded an investigation by the Genesee County health department into the source of a major legionnaires’ outbreak in the area. The county’s investigation into the outbreak is ongoing, he said.

Schuette has been criticized for his appointment of special counsel in the investigation, Todd Flood, who has previously donated to Schuette’s campaigns, as well as to Snyder. The attorney general’s office has countered that criticism by highlighting Flood’s donations to both Republicans and Democrats.

Schuette was initially asked last fall by a state lawmaker to launch an investigation into Flint, but the attorney general declined, citing the multiple federal and state investigations already under way. But as public outcry grew, Schuette decided otherwise and announced in January the assembly of what he described as a “top-shelf team” of investigators to review what happened in Flint.

Snyder called news of the charges “deeply troubling”.

“I have said all along that bureaucrats making bad decisions failed the people of Flint,” he said. “The charges filed today raise what happened to a whole new level and we take that very seriously.

“We will vigorously pursue any evidence of wrongdoing and we will hold people accountable.”

Arena said the investigation is in its early stages and will be all-encompassing.

“Nobody’s off limits,” he said.

Still, Flint residents said high-level officials – including Snyder – should be charged.

“I’m organizing water deliveries while dealing with health issues from the water crisis,” said Melissa Mays, who is also a plaintiff in several lawsuits filed against state and local officials, in a statement. “I’m happy to see criminal charges, but Governor Snyder should also be on the list.”

“They’re starting with the peons,” said Keith Pemberton, 67. “And they should be starting from the top and working their way down.”

Pemberton, a Flint resident of 14 years, stood on Saginaw Avenue as the press conference unfolded, holding a sign that read: “Snyder is a murderer.” While vehicles drove by and honked their cars in support, he said his grandkids have tested positive for elevated blood lead levels.

“How do you think we feel, knowing that our grandkids are going to be mutilated by the effects of lead?” he said.