Presidential hopeful Elizabeth Warren and a handful of other Democratic lawmakers are demanding an investigation into the crafting of a rule that would allow teens to operate lifts in nursing homes.

In a Monday letter to the Office of the Inspector General, the Massachusetts senator expressed doubts about the process used by the Department of Labor to craft the proposed law change. Proposed in September, the “Teen Healthcare Worker Rule,” as it’s been called, would allow 16- and 17-year-old employees in nursing homes and other healthcare facilities to operate power-driven patient lifts. Warren and colleagues this week poked holes in the DOL’s failure to include in its public docket a 2012 survey of schools, used to support the need for the rule change, prior to the Dec. 11 comment deadline.

“DOL’s actions in the course of this rulemaking raise serious concerns around a lack of required transparency,” wrote Warren, currently a Senator from Massachusetts, who was joined by House lawmakers Bobby Scott (D-VA), Rosa DeLauro (D-CT), Mark Takano (D-CA), and Lucille Roybal-Allard (D-CA). “DOL’s failure to publicly disclose the 2012 survey during the public comment period deviates from EO transparency requirements that ensure the public is able to make meaningful, informed comments on proposals.”

The National Employment Law Project also raised concerns about the same survey in December. That New York think tank noted that the survey is years old and represented a “scant” 22 vocational programs.

Provider groups — which have supported the Teen Healthcare Worker Rule — meanwhile, pushed back against critics last month. Members of the provider and business communities have favored the chance to broaden employment opportunities for teens in order to address the industry’s ongoing staffing challenges.

Warren and colleagues are demanding that the Office of the Inspector General conduct an audit of the ongoing rulemaking process, including whether Labor complied with public transparency requirements, and if it adhered to its own data quality guidelines, according to the letter. The final rule has yet to be published, after public comment ended in December. Worker safety advocacy groups have threatened to sue if it becomes law.