Six U.S. senators, including Democrat whip Dick Durbin and Elizabeth Warren, wrote public letters to tobacco giants Reynolds American and Altria on Thursday to ask questions about donations and lobbying of the Trump administration, saying the companies had enjoyed a "lucrative payday" after spending millions to curry favor with the president.

The letter came after the U.S. ‌Food and Drug Administration laid out a new "enforcement discretion" policy in which ​it will allow some manufacturers to sell vapes and nicotine pouches without the legally required license. The move could unleash hundreds or more vapes onto ⁠the market, and followed pressure from the White House for change.

It also followed ​political donations from Reynolds, the U.S. subsidiary of British American Tobacco, and Altria as recently ⁠as April, and a meeting between President Donald Trump and tobacco executives in May.

"Money well spent," the letters, dated June 4, said, adding that the donations and lobbying had enabled tobacco makers to circumvent federal ‌laws to sell addictive vapes, harming the FDA's independence.

"But for you and ​your shareholders, this ‌was a lucrative payday after years of unsuccessful legislative and regulatory efforts to weaken federal tobacco oversight," it said, asking for details ‌on donations, meetings and products that will benefit from the change.

Reynolds and the White House did not immediately respond to requests for comment.

An Altria spokesperson said "the guidance ⁠is an important step toward addressing the ‌illicit market by pairing enforcement with ⁠expansion of a legal, regulated marketplace for smoke-free products," adding that the company is reviewing the implications of its ⁠product ⁠strategy and will continue to compete within the FDA regulated marketplace.

The companies have complained for years that FDA policy has helped ‌fuel a booming market for unlicensed devices mostly from China. Reynolds estimates this illegal market is worth some $9.41 billion.

The companies have launched lobbying campaigns and court cases, put sales targets ‌on hold ​and threatened to launch their own ‌unlicensed products to compete.

Tobacco companies have already announced plans to launch new products following the "enforcement discretion" policy.

The letters were signed by Democrat senators Durbin ​of Illinois, Warren and Edward Markey of Massachusetts, Jeff Merkley of Oregon, Richard Blumenthal of Connecticut, and Jack Reed of Rhode Island.