(CNN) After calling on his 2020 Democratic opponents to reject money from insurance and drug companies, Sen. Bernie Sanders will return donations he received that violate that pledge, his campaign said Thursday.

The pledge, announced on Wednesday, calls on 2020 campaigns to refuse "contributions over $200 from the PACs, lobbyists, or executives of health insurance or pharmaceutical companies," except for "rank-and-file workers employed by pharmaceutical giants," according to a campaign statement.

"It seems to me that if we are going to break the stranglehold of corporate interests over the health care needs of the American people, we have got to confront a Washington culture that is corrupt that puts profits ahead of the needs of the people," Sanders said during a speech on his "Medicare for All" proposal in Washington, DC.

"I am calling on every Democratic candidate in this election to join me in rejecting money from the insurance and drug companies," Sanders added.

A CNN review of the campaign's publicly available donation history found the campaign has received at least six contributions of more than $200 from donors who did not list their official titles when giving money, but whose job descriptions contradict the pledge put forth by Sanders.

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