Authorities search for missing 11-year-old girl in Texas 2:20

(CNN) --

The only trace in the disappearance of Audrii Cunningham, a girl just 11 years old, could be a red "Hello Kitty" backpack that she had to take with her to school.

Cunningham disappeared after leaving her home to catch the school bus on the morning of Thursday, February 15, in the small East Texas town of Livingston, about 70 miles northeast of Houston.

Audrii never got on the bus, the Polk County Sheriff's Office reported. However, "a small backpack that probably belonged to a minor was located near the Lake Livingston dam," the entity said.

A man arrested in an unrelated aggravated assault case is now believed to be "one of the persons of interest involved in the disappearance" of the girl, the sheriff's office said. However, Cunningham's whereabouts remain a mystery.

Audrii Cunningham. (Credit: Polk County Sheriff's Office)

This is what we know about the case so far.

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He never came to school that day

Audrii Cunningham was last seen around 7 a.m. Thursday near her home on Lakeside Drive, the Polk County Sheriff's Office said.

The house is near Lake Livingston, "one of the largest reservoirs in the state, with more than 335 kilometers of surface area," according to the Texas Parks and Wildlife agency. "The lake is a reservoir of the Trinity River, and supplies water to the city of Houston and other cities in East Texas," the entity added.

  • Police search for an 11-year-old girl missing in Texas; there is a man detained

According to the sheriff's office, "Audrii should have caught the school bus at her neighborhood stop. However, school officials informed the sheriff's office that the school bus did not pick up Audrii, nor did she show up at school." ".

Audrii's family reported him missing after he did not return home from school. A search involving multiple agencies was activated, including the Texas Rangers, Texas Department of Public Safety, Livingston Police Department, Texas State Guard and several local fire departments, the sheriff's office said.

They may have found his backpack

This Friday, "a small backpack likely belonging to a juvenile was located near the Lake Livingston Dam," the Polk County Sheriff's Office said.

Previously, authorities said Audrii was carrying a bright red "Hello Kitty" backpack.

However, the investigation "remains active and ongoing," the sheriff's office said.

Authorities are searching for Audrii Cunningham, the 11-year-old Texas girl who disappeared Thursday, February 15, in Polk County. (Credit: KHOU)

"Criminal action may be a factor"

Investigators identified a 42-year-old man "as one of the persons of interest involved in the disappearance" and believe his dark blue 2003 Chevrolet Suburban was involved, the sheriff's office said.

Authorities arrested the man Friday on an unrelated charge of aggravated assault. However, they have not given details about how the man could be related to the disappearance of Audrii Cunningham.

"Our main goal and hope is that we bring Audrii home safely," said Texas Department of Public Safety spokesman Lt. Craig Cummings. "But we are also aware that criminal action may be a factor."

"This is the kind of thing you see on television."

Audrii Cunningham's mother, Cassie Matthews, said she always ached for the parents of missing children she heard about through the news.

"This is the kind of thing you see on television, and you can only imagine what the family and the parents are going through," Matthews told CNN affiliate KPRC.

Now, she is one of those parents.

"There are no words to describe it. There is not a single feeling. It's a roller coaster. You're broken, you're angry, you're empty. And right now, I'm empty," Matthews said.

"He has so many opportunities ahead of him, and he deserves every right to be able to achieve them."

Audrii is white, with blonde hair and blue eyes. She is about 1.2o meters tall and weighs about 34 kilograms, the sheriff's office said. The girl was last seen wearing black pants, a black hoodie with white lettering, and black high-top sneakers.

Anyone with information in this case is asked to immediately contact the Polk County Sheriff's Office at 936-327-6810 or submit an anonymous tip online. 

CNN's Rosa Flores, Chris Boyette and Joe Sutton contributed to this report

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