Republicans and Democrats brawled Wednesday morning over GOP efforts to subpoena the names of graduate students and researchers as part of their investigation into Planned Parenthood.

The House Select Investigative Panel on Planned Parenthood opened with its first hearing on Wednesday, focusing on the issue of bioethics and fetal tissue research. But before the panel could get to the hearing, Democrats and Republicans bickered over the GOP subpoenas, and Democrats argued the Republican effort was just a partisan witch hunt that had no bearing on the investigation.

"To date, you have refused to explain how this information is pertinent to the investigation," said Rep. Jerrold Nadler, D-N.Y., who said that Republicans didn't alert Democrats per House rules about the subpoenas.