The members are all Democrats except Sanders, who's an independent.
Amazon shot back Tuesday, saying Sanders has an open invitation to visit its warehouses "but to date has never stepped foot in one of our buildings."
The company said if Sanders had seen the facilities, he'd have learned that the company already implemented multiple layers of safety protocols at its warehouses.
"The allegations outlined in this letter are not an accurate portrayal of activities in our buildings," Amazon said, adding that people as young as 6 can tour the buildings to see for themselves.
The Congressional request continues long-running criticisms of how Amazon operates its warehouses, with years of news reports detailing employees being overworked, forced to move faster and closely monitored.
Sanders' criticisms follow his repeated attacks against Amazon last year, when he called on the company to raise its minimum wage.