Guards at a Kansas prison housing some of the most dangerous criminals say there were two previously unreported disturbances during which inmates took control of the yard for hours before an third uprising that was disclosed last month.

Two corrections officers and a person with access to emergency logs, who spoke to AP on condition of anonymity because they feared reprisals from their employer, say low staffing, overcrowding and 16-hour shifts created dangerous conditions at the El Dorado  Correctional Facility.

They say inmates took over the yard for hours during a disturbance the week of May 8 and on June 24. Neither incident has been disclosed by the Kansas Department of Corrections. A third incident on June 29 was revealed when inmates got a cellphone and called relatives.