Of course they block it.
Check it out:

Democrats have blocked a Republican push for a joint House-Senate investigation of the deadly 2012 attack on the U.S. diplomatic mission in Benghazi, Libya.

Sen. Ted Cruz sought support on Monday for the Senate to participate in the inquiry. The Texas Republican argued that persistent questions still remain, including whether President Barack Obama slept the night of the attack.

Democratic Sen. Bob Menendez of New Jersey objected, saying the eighth probe is politically motivated and without merit.

The House is moving ahead with a special select committee to investigate the Sept. 11, 2012 assault in which U.S. Ambassador Chris Stevens and three other Americans were killed.