(CNN)County administrators in Colorado have opened an investigation into an election official after employees complained she was pressuring them not to cooperate with a joint local, state and federal criminal investigation into an election system security breach discovered last month, a source told CNN.

Deputy clerk Belinda Knisley of the Mesa County Clerk and Recorders office has been placed on paid administrative leave due to a "confidential personnel matter," CNN previously reported. A source in the Mesa County government tells CNN that the "confidential personnel matter" refers to an open county human resources investigation in which Knisley is accused of pressuring fellow clerk employees -- her subordinates -- not to cooperate with the criminal investigation into the breach.

When Knisley caught wind of the HR investigation, the source said that Knisley also then pressured employees not to cooperate with it.