Valley Springs, California (CNN) -- Investigators interviewed registered sex offenders in the Northern California community where an 8-year-old girl was stabbed to death, but officials won't say if sexual assault is part of the unsolved crime.
"They have been interviewed and in some cases they have been photographed and in some cases they have been searched," Calaveras County Sheriff's Capt. Jim Macedo said late Monday night.
So far, despite an extensive manhunt and beefed-up security at schools in Valley Springs, authorities don't have enough information to name a suspect or even create a composite sketch in the death of Leila Fowler.
"This is a sad time," said Calaveras County Sheriff Gary Kuntz. "We will not rest until we capture the responsible person."
Leila, an 8-year-old known for her bubbly personality, was stabbed to death at her home over the weekend.
Her 12-year-old brother says he saw an intruder in the family's home before finding his sister suffering from stab wounds.
All police have to go with is a sketchy description: a white or Hispanic male with a muscular build, about 6 feet tall, wearing a black long-sleeved shirt and blue pants.
The thought of a killer on the loose in Valley Springs, a small town about 60 miles southeast of Sacramento, has many on edge.
"When your husband is walking around with a pistol on his hip to protect his family you get a little scared," one shaken woman told CNN affiliate KRON.
Police say Leila and her brother were home alone on Saturday when he saw an intruder leaving the house.
He then found his sister stabbed and severely wounded. She died minutes after arriving at the hospital, authorities said.
Since then, police have been running down leads, searching in attics, storage sheds in the mountainous, rural community.
Authorities have also combed the home and the neighborhood for evidence.
"We did collect fingerprints during that search," Macedo said, "and we did collect what we believe to be DNA. Those prints and DNA will hopefully be processed within the next week."
All around Valley Springs, purple ribbons, Leila's favorite color, are tied to stop signs and at schools as the small community tries to find a way to support her crestfallen parents.
The couple was at a Monday evening news conference listening intently as authorities said they would do everything they could to catch the killer.
The mother cried throughout the briefing and gasped as a detective read the results of the young girl's autopsy.
She died, authorities said, of shock and hemorrhages caused by multiple stab wounds.
The parents were too overwhelmed to speak at the news conference.
But earlier Monday, the mother spoke to CNN via her Facebook page.
"We are devastated," Crystal Walters said. "She didn't deserve this. ... She was so full of life."
A candlelight vigil is planned for Tuesday evening.
CNN's Paul Vercammen reported from Valley Springs, California. CNN's Lateef Mungin reported and wrote from Atlanta.