Lisa Rachelle Snyder, 36, was arrested on Monday and charged with first-degree murder, third-degree murder and endangering the welfare of children in relation to the deaths of her kids Conner, eight, and Brinley, four, who were found hanged in her basement on September 23.
In a separate incident, Snyder was also charged with sexual intercourse with a dog.
Conner and Brinley were found unresponsive in the basement of the family home. They were revived by paramedics but later died in hospital.
In a call to emergency services Snyder told a dispatcher that Conner 'made threats of doing this but didn't want to go alone.'
Snyder then created a Facebook page in their memory in which she documented how hard life was without her kids.
During the course of their investigation police seized electronic devices from the family home including mobile phones and computers. They also said they were looking for a dog that had been given away.
Local reported Jim Vasil, who works for WFMZ in Pennsylvania, US, where Snyder lives, reported that the police found photograph evidence relating to the abuse of the dog while investigating the deaths of Snyder's children.
Officials are expected to release more details of Snyder's arrest at a press conference.