The chairman of the House's oversight committee is launching an investigation into three drug companies for allegedly obstructing a congressional probe into generic drug prices.

Rep. Elijah Cummings Elijah Eugene CummingsBlack GOP candidate accuses Behar of wearing black face in heated interview Overnight Health Care: US won't join global coronavirus vaccine initiative | Federal panel lays out initial priorities for COVID-19 vaccine distribution | NIH panel: 'Insufficient data' to show treatment touted by Trump works House Oversight Democrats to subpoena AbbVie in drug pricing probe MORE (D-Md.), chairman of the House Oversight and Reform Committee, and Sen. Bernie Sanders Bernie SandersThe Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power Bernie Sanders: 'This is an election between Donald Trump and democracy' The Hill's 12:30 Report: Trump stokes fears over November election outcome MORE (I-Vt.), the ranking member on the Senate Budget Committee, said Tuesday they would investigate an apparent coordinated obstruction campaign on the part of Heritage Pharmaceuticals, Mylan N.V. and Teva Pharmaceuticals.

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“Not only did your company’s apparent obstruction undermine our investigation, but it may have caused further harm to patients and health care providers by delaying the discovery of evidence about the companies’ price-fixing,” Cummings and Sanders wrote in letters to the firms.

"Furthermore, obstructing or evading a Congressional investigation, including withholding or concealing information, is a violation of federal law.”

Cummings and Sanders first requested documents from the companies in 2014 detailing "staggering" price increases of generic drugs.

None of the companies produced any documents despite "repeated inquiries," Sanders and Cummings wrote.

In May, Connecticut and 43 states filed a complaint alleging the three companies, and other drug makers, illegally colluded to keep generic drug prices high.

The lawsuit states that Heritage, Mylan and Teva also coordinated their responses to Cummings's 2014 investigation, with one representative writing in an email that the "consensus at this point is that the responses will be polite f-u letters."

Cummings and Sanders are requesting the original documents they asked for in 2014, as well as all communications between the three companies related to that investigation.

Cummings and Sanders also asked the Department of Justice (DOJ) last month to open an investigation into whether the three companies obstructed their probe.

The DOJ has already been investigating price fixing and other anticompetitive conduct in the generic drug industry.

Heritage in May agreed to pay more than $7 million to resolve criminal and civil price-fixing allegations.