Federal mine-safety officials said Thursday that they closed six Kentucky mines and issued more than 1,000 citations for safety violations as a result of a nationwide sweep last month of 57 coal mines with a history of repeat safety violations.

The five-day inspection blitz was in response to the April 5 explosion that killed 29 at Massey Energy Co.'s Upper Big Branch mine in West Virginia, which had been cited repeatedly for dangerous conditions.

Two...