An Amazon spokesperson told CNBC that the company requests safety documentation “very shortly” after a product is listed by a third party seller. In an email statement, the company said it regularly contacts selling partners to request safety documentation. Sellers who do not provide the required documentation are removed immediately.

That practice leaves a window in which unsafe toys could potentially be sold to consumers. To make matters worse, Amazon recently came under fire for selling thousands of items that federal agencies had deemed unsafe. After a Wall Street Journal investigation discovered everything from unregistered pesticides to banned toys on the site, three senators wrote a letter asking Amazon CEO Jeff Bezos to launch a “sweeping internal investigation” into the company’s safety policies. It’s unclear if Amazon has taken any steps since then to improve consumer safety, but now, it will likely be under increased pressure to do so.

Authored by Senate commerce committee members Bob Menendez (D-NJ), Ed Markey (D-MA) and Richard Blumenthal (D-CT), the letter also called for the ecommerce giant to immediately remove the illicit items. “Unquestionably, Amazon is falling short of its commitment to keeping safe those consumers who use its massive platform. We call on you to immediately remove from the platform all the problematic products examined in the recent WSJ report, explain how you are going about the process, conduct a sweeping internal investigation of your enforcement and consumer safety policy; and institute changes that will continue to keep unsafe products off your platform,” wrote the lawmakers. Earlier this month, Menendez and Blumenthal sent a letter to the retail giant inquiring about its “Amazon Choice” program and why faulty or inferior products sometimes receive the touted classification.

The WSJ investigation found at least 2,000 listings on Amazon for toys and medications that lacked warnings about health risks to children. Reporters also unearthed toxic paint strippers, infant sleeping mats linked to suffocation, dietary supplements containing illegal prescription drugs, toys containing lead and products that falsely stated they were cleared by a federal agency.

The report recounted an incident in which a 23-year old wearing a helmet purchased on Amazon died in a 2014 motorcycle crash. The helmet, which came off of the man during the crash, had been fraudulently listed as certified by the Department of Transportation.

The senators also asked Amazon for an explanation of why its current safety protocols failed, and what it will do to prevent selling unsafe products in the future. In response to the WSJ article, Amazon published a blog post about its existing safety and compliance program but made no promises that it would change its protocols.

According to CNET, Amazon said it plans on answering the questions posed by senators in the letter. The WSJ reported today that Amazon appeared to remove or modify some of the dangerous items, but some of them have since resurfaced under new listings.