New York's top prosecutor has accused Amazon of falling short of health and safety laws in its response to the coronavirus pandemic.
In a lawsuit, Attorney General Letitia James said Amazon had displayed a "flagrant disregard" for the rules and illegally retaliated against workers who raised concerns.
Amazon last week attempted to block the lawsuit with its own legal action.
It said Ms James was applying "an inconsistent and unfair" standard.
"We care deeply about the health and safety of our employees, as demonstrated in our filing last week, and we don't believe the Attorney General's filing presents an accurate picture of Amazon's industry-leading response to the pandemic," spokeswoman Kelly Nantel said in a statement.
'Danger to public health'
Amazon faced criticism from workers around the world last year over its response to the coronavirus pandemic. In France and Spain, officials forced the firm to make changes after unions filed complaints.
Ms James said her inquiry into conditions at two warehouses in New York City found Amazon implemented a "deficient" programme to trace the contacts of infected workers and did not follow rules requiring companies to shut and disinfect areas that had been visited by a sick person, among other violations.
She said the firm "cut corners" when it came to steps that would have hurt its sales volume - and profit.
"Amazon's flagrant disregard for health and safety requirements has threatened serious illness and grave harm to the thousands of workers in these facilities and poses a continued substantial and specific danger to the public health," she said in the filing.
Ms James launched her investigation last March after numerous complaints about the lack of precautions for workers n New York, then the epicentre of America's coronavirus outbreak.
The probe later expanded to include concerns about retaliation after Amazon fired some of the workers, including Christian Smalls, who spoke out about the issues.
"While Amazon and its CEO made billions during this crisis, hardworking employees were forced to endure unsafe conditions and were retaliated against for rightfully voicing these concerns," she said.
"Since the pandemic began, it is clear that Amazon has valued profit over people and has failed to ensure the health and safety of its workers."
In its complaint last week, Amazon said Ms James lacked oversight over the workplace issues, which it said are governed by national labour laws.
It also accused her of ignoring the steps the company has taken to protect its workers, pointing to a 30 March city inspection inspection of its warehouse in Staten Island, New York, which concluded that "there were absolutely no areas of concern".
The rate of infection among Amazon staff in New York is half that of the area's general population, it added.
Amazon said that it fired Mr Smalls for violating requests that he quarantine after being exposed to the virus.