(CNN) -- A second Maryland woman has been charged with murder in connection with the Friday stabbing deaths of two children during an exorcism attempt, authorities said.
Two children died of multiple stab wounds and two others are hospitalized with undisclosed injuries, police said.
Monifa Denise Sanford, 21, was charged with two counts of first-degree murder and two counts of attempted first-degree murder, Montgomery County Police said.
Earlier, authorities announced that the children's mother, Zakieya L. Avery, 28, also faces the same charges. Police said Saturday that Avery stabbed two of her children to death and wounded two others while attempting an exorcism.
Sanford was briefly hospitalized after the incident and was charged after she was released. Police believe she is not related to the family, but lived at the same residence in Germantown.
Norell Harris, 1, and his sister, Zyana Harris, 2, suffered fatal stab wounds while their siblings, who are 5 and 8, were hospitalized, authorities said.
"Cases like this are heartbreaking," county Police Chief Tom Manger said. "Our thoughts are with the family and friends of the victims."
Police said they found the four children Friday morning after a neighbor called 911 to report suspicious activity at the home. The neighbor reported seeing a car with a door open and a knife next to it.
Exorcism is a ritual aimed at defeating purported evil spirits or demons. Authorities did not provide details on why they suspected exorcism.
"Investigators have learned that the two defendants believed that they were performing an exorcism. The investigation into this motive and other aspects of the crime continue at this point," police said.
Police were called to the home Thursday over reports of an unattended child in a car. By the time they got there, the child was not in the car and no one came to the door, authorities said.
"Prior to officers arriving, two women exited the townhouse, retrieved the child and re-entered the home," Montgomery County Police said. "Officers attempted to speak with the residents, but received no response at the door. "
After the neighbor's call, authorities notified county child protective services and asked them to follow up. It's unclear whether they did.
Both women are being held without bail. Information on their attorneys was not immediately available.