Washington DC - Key Democratic lawmakers overseeing the Treasury Department called Tuesday for an investigation into how Elon Musk and his aides gained access to the agency's payments system – a move that also triggered a lawsuit.

In a letter to the congressional watchdog, the Government Accountability Office (GAO), Senators Elizabeth Warren and Ron Wyden asked for a probe into reports that Treasury Secretary Scott Bessent had granted Musk and his government efficiency group permission to get into the system.

Musk, the world's richest person, is leading President Donald Trump's federal cost-cutting efforts under the so-called Department of Government Efficiency (DOGE).

The Treasury's closely guarded payments system handles the US government's money flow, including $6 trillion annually for Social Security, Medicare, federal salaries, and other critical payments.

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"GAO must investigate and determine who was granted access to these systems, why and how this access was granted, and the implications for the nation's economic and national security," wrote Warren and Wyden.

Warren is the top Democrat on the Senate Banking Committee, while Wyden is that of the Senate Finance Committee.

The pair questioned the process by which Musk's team gained access to Treasury systems, raising privacy concerns as well.

In a separate letter to Trump Tuesday, other Democratic policymakers similarly expressed concern over DOGE's work involving government data and facilities.

Their letters came shortly after labor unions and a grassroots advocacy group filed a lawsuit on the matter.

The suit called on a federal judge to declare it illegal for Musk or others from DOGE to get personal information about taxpayers and to block the Treasury Department from letting that happen.

In a post on X, the social media platform that he owns, Musk said Monday that the "only way to stop fraud and waste of taxpayer money is to follow the payment flows and pause suspicious transactions for review."

Musk's access to the payments system was approved by Bessent and made possible when a career official was put on administrative leave Friday after refusing to allow entry, according to the lawsuit.