A woman was arrested after her two daughters were found stabbed to death, authorities said.

The girls, ages 8 and 5, were found lying next to one another in a bedroom of the mobile home they shared with their mother in Macomb Township, about 30 miles northeast of Detroit, Macomb County Sheriff Mark Hackel said. Police said they recovered several large bloody knives.

"It's an extremely horrific scene," Hackel said.

Police were notified Sunday night by the 30-year-old woman's sister, who found the suspect sitting alone amid the carnage. The sister was told by the suspect she had "hurt her kids," Hackel said. The stabbings took place late Saturday or early Sunday, he said.

Click here for FOXNews.com's Crime center.

Three small dogs and a pet mouse were also found dead in the home, the sheriff said. Police said the suspect suffered a self-inflicted, minor stab wound to her arm.

Hackel said the woman apparently had no criminal record but may have had "some mental health issues."