Law enforcement agencies are searching for a suspect described as a 6-foot-tall man with a muscular build. He was last seen wearing a black long-sleeved shirt and blue pants. The suspect is considered "armed and dangerous," according to police.
Police have been searching Fowler's home in Valley Springs, Calif., a rural town 60 miles southeast of Sacramento, and the surrounding areas.
"We did collect some fingerprints during that search and we also collected what we believe to be DNA," Calaveras County Sheriff's Capt. Jim Macedo said at a news conference. "We're searching extensively into attics and storage sheds. It is a difficult area to search."
The area has a lot of empty homes and rocky areas.
Police said Leila's brother is not a suspect at this time, but they have been interviewing him.
"We are continuing to talk to him, which would be normal because he was the last person with the child," Macedo said.
Authorities are also asking for any information on anyone who may have left town unexpectedly after the crime or has unexplained injuries, according to an alert on the Calaveras County Sheriff's Office website.
Anyone with information is asked to contact a tip line at 209-754-6030.
Additional reporting by ABC News' Alyssa Newcomb.