Authorities are searching for a missing 3-year-old West Virginia girl in what a national expert called an aggressive and extraordinary effort to find her.

Aliayah Lunsford disappeared from her home in Bendale, W.Va., Saturday morning, and hundreds of people have been helping local, state and federal authorities try to locate her.

FBI investigators have gone door to door. Dive teams have searched an underwater grid in the West Fork River. The National Center for Missing & Exploited Children, which listed the missing child as "endangered missing" on its website, dispatched a member of Team Adam, retired investigators who advise local officers.

"The level of response has been extraordinary," said Ernie Allen, president of the national group. "There have been massive resources devoted to this.

"There's no doubt in our mind that the sheriff's department, the State Police, the FBI and we are doing everything possible to find this child and bring her home," he said.

Lena Lunsford told police she'd checked on her daughter around 6:30 a.m. Saturday, then discovered her missing three hours later.

Aliayah is about 3 feet tall and 35 pounds, with brown hair and brown eyes. Her ears are pierced and she is missing her top four front teeth, according to the NCMEC website. She was last seen in purple pajama bottoms and a pink sweatshirt.

Allen said it's too soon to give up hope. Children often wander farther than people think they can, and some can be missing for days and turn up safely.

On Monday, two Kentucky firefighters found a 7-year-old autistic boy who went missing the same day as Aliayah. Randall Leon Chesser had wandered some 3 miles from his home in Willisburg, Ky., but was found unharmed.

Click for more on the disappearance of Aliayah Lunsford from the National Center for Missing & Exploited Children

The Associated Press contributed to this report.