Republican lawmakers are stepping up their campaign to gain access to the survivors of the Benghazi terror attack, with one claiming the Obama administration is engaging in a “cover-up” and another threatening to bring “legal charges.”

The frustration is mounting six months after the Sept. 11 attack on a U.S. consulate in Libya. Republicans have sparred with the Obama administration over a range of issues — from the faulty explanation over what caused the attack to the warning signs missed in advance of it — but have focused recently on the surviving victims. They say they’ve been stonewalled in their attempts to get a list of survivors and speak with them.

Rep. Frank Wolf, R-Va., told Fox News on Tuesday that some have been at a Washington-area military hospital since the attack, saying their injuries must be “serious.”