The letter, addressed to Chief Executive Jeff Bezos, adds to public scrutiny Amazon is facing over the dismissal, at a time when the company is racing to update safety protocols, keep warehouses open and ship essential goods to shoppers who are shut indoors.
Amazon employee Christian Smalls came to the company's Staten Island, New York, warehouse on March 30 for a small protest he helped organize, which in part called for the site's closure. Workers feared infection after a colleague had fallen ill to the novel coronavirus, cases of which have now been reported among staff at more than 50 Amazon warehouses, according to the New York Times.
The virus has infected more than 1.4 million people globally.
Amazon said it fired Smalls, who had contact with the virus patient, after he violated a paid quarantine to join the protest. The dismissal prompted New York City's mayor to announce a probe and the state's attorney general to demand a U.S. labor board investigation.
In Wednesday's letter, senators led by Cory Booker of New Jersey questioned the order of events. They cited a media report suggesting that Smalls' two-week quarantine may have come after Smalls "had begun organizing their colleagues to demand more workplace transparency and stronger workplace protections." The quarantine should have ended five days before the protest based on a possible March 11 exposure, the letter said, citing the media report.
"The right to organize is a bedrock of our economy, responsible for many of the greatest advances achieved by workers over generations," the letter said.
Amazon said Smalls' contact with the diagnosed worker was well after the 11th and that on March 28 he was told to go into quarantine.
The company said it fired Smalls because he put others' health at risk, not because he organized a protest.
Amazon said it is taking "extreme" measures to keep staff safe while shipping goods to U.S. households, the vast majority of which are under a stay-at-home order. On top of site cleaning, it is requiring temperature checks and social distancing, and is making masks available at all U.S. and European warehouses, the company said.
Leaked notes from an Amazon executive meeting have added to blowback over the firing. In the notes, Amazon's general counsel described Smalls as "not smart, or articulate."
He later issued a statement saying frustration over the health risks created by Smalls had clouded his judgment.
The other signatories to the senators' letter, which referenced the leaked notes, were Robert Menendez, Sherrod Brown, Richard Blumenthal and Kirsten Gillibrand.