FILE PHOTO: Jeff Bezos, founder of Amazon and Blue Origin speaks during the JFK Space Summit, celebrating the 50th anniversary of the moon landing, at the John F. Kennedy Library in Boston, Massachusetts, U.S., June 19, 2019. REUTERS/Katherine Taylor

WASHINGTON (Reuters) - Three U.S. senators on Thursday said Amazon.com Inc should stop working with delivery contractors that violate labor laws by imposing unfair conditions on drivers delivering packages for the e-commerce company.

The senators, in a letter bit.ly/2lSfcDP to Chief Executive Officer Jeff Bezos, responded to reports that alleged Amazon pressured contractors and more broadly avoided regulatory scrutiny.

Amazon said in a statement it had taken steps to ensure “a strong safety and labor compliance record across our transportation network of employees and contractors, and we continue to drive improvements that benefit our transportation providers, our customers and the public.”

The company added it has “strict requirements for safety and labor wages and working conditions that meet or exceed the law.

We also require comprehensive insurance, competitive wages, working hours and numerous other safeguards for our delivery service providers and regularly audit to ensure compliance.”

The letter was signed by Democratic presidential hopeful Elizabeth Warren, Connecticut Senator Richard Blumenthal and Ohio Senator Sherrod Brown.

Buzzfeed on Aug. 31 said Amazon was creating what it called exploitative conditions for driver contractors by pushing them to deliver upwards of 250 packages a day.

Amazon had told Buzzfeed it expects its delivery operators to comply with labor laws.

Democratic presidential candidate Andrew Yang had last week also called for increased regulation of Amazon’s delivery network.