A 10-year-old girl was found dead of an apparent suicide Sunday in Santa Ana, California, authorities said.

The girl was discovered by her 9-year-old sister, according to the Santa Ana Police Department.

"As part of our investigation we are looking into the unconfirmed rumors there may have been some bullying involved," a police spokesman told NBC News Tuesday. "We are looking into that, social media, electronic devices, etc."

Hazard Elementary School in Santa Ana, Calif. Google Maps

Crisis counselors were at Hazard Elementary School on Tuesday, where the girl was a student.

A spokeswoman for the Garden Grove Unified School District told NBC News it is "deeply saddened by the tragic passing" of one of its students.

"Santa Ana police have informed us that they are assessing any and all factors that may have contributed to this tragedy," the spokeswoman said in a statement.

The district also said it recently launched a wellness campaign aimed at increasing awareness and ensuring all students, staff and families have access to mental health and wellness support.

If you or someone you know is in crisis, call the National Suicide Prevention Lifeline at 800-273-8255, text HOME to 741741 or visit SpeakingOfSuicide.com/resources for additional resources.