Missouri Sen. Claire McCaskill (D.) launched an investigation this week into the country's leading opioid manufacturers, including one that is run by the daughter of one of her Democratic colleagues.
Among the five companies initially alerted to McCaskill's investigation was Mylan, a leading opioid manufacturer that is run by Democratic Sen. Joe Manchin's (W.Va.) daughter Heather Bresch, who is the company's CEO.
In a statement, McCaskill put blame on the marketing campaigns put in place by executives in pharmaceutical companies such as Mylan for allowing the opioid epidemic to become the crisis it is today.
"All of this didn't happen overnight," McCaskill said. "It happened one prescription and marketing program at a time."
"The vast majority of the employees, executives, sales representatives, scientists, and doctors involved with this industry are good people and responsible actors, but some are not. This investigation is about finding out whether the same practices that led to this epidemic still continue today, and if decisions are being made that harm the public health," she said.
This is not the first time that Manchin's daughter has been targeted by his Democratic colleagues.
Another instance came last year after it was reported last year that Mylan was overcharging for its EpiPen, a lifesaving device for individuals with severe allergies.
Democratic Sens. Richard Blumenthal (Conn.) and Amy Klobuchar (Minn.) called for an investigation into possible anti-trust violations by Bresch and Mylan.
Sen. Ron Wyden (D., Ore.) accused Mylan of "bilking taxpayers out of millions of dollars."
Bloomberg reported that it would be "awkward" for Bresch to be called to testify on Capitol Hill given that her father is a member of the Senate.
Manchin has been criticized for his lack of focus on pharmaceutical companies in his response to the opioid crisis.