“The girls are still missing but at this point in the investigation, it is believed the girls ran away from home," the Riverside Police Department said in a statement Monday.
Police called on the public to help with with the search.
“Extensive efforts have been made by police, family and friends to locate the two girls with no success," authorities said.
Bolt and Tourdot had been close friends for weeks when Bolt asked her parents if she could spent the night at Tourdot's house.
Tourdot's mother said she fell asleep at around around 10:30 or 11 p.m. on Saturday and woke up to find that the girls had disappeared.
Police said they believed that the girls, who were last spotted at the Riverside Plaza Mall on Sunday afternoon, had run away.
Bolt's father, Donald, told KABC that he didn't think his daughter had any reason to runaway.
"We just all enjoy everyday, I mean, we get along, we look forward to the next video games, the next PewDiePie on YouTube, you know. Unfortunately, I think these two girls just got into a little bit of trouble," he said.