A broadened recovery effort is underway in South Dakota this weekend for a 9-year-old girl who has been missing since last Sunday.

Authorities say Serenity Dennard ran away from the Black Hills Children’s Home that day and entered the surrounding forest. The home is in Rockerville, southwest of Rapid City.

The Pennington County Sheriff’s Office says it’s unlikely that the girl survived if she remained outdoors because of frigid weather in the region in recent days. The girl was not dressed for cold weather when she left around 10:45 a.m., authorities say.

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On Friday, search crews used specially trained dogs to help track down the child. A helicopter was also being deployed.

The effort was delayed Wednesday and Thursday because of a winter storm in the area.

"Our plan is moving forward for today, and now we're just hoping for the results that we're looking for," Willie Whelchel, chief deputy with the Pennington County Sheriff's Office, told the Argus Leader of Sioux Falls.

As many as 40 people have been participating in the recovery efforts. The girl was described as being 4-feet-9, weighing 90 to 100 pounds, with blonde hair and blue eyes.

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Staff at the children’s home waited more than 90 minutes to alert 911 after realizing the child was missing, the Rapid City Journal reported.

“We immediately conducted a thorough search of our grounds and buildings,” Bill Colson, executive director of the Children's Home Society, which operates the home, told the Associated Press. “When we were unable to find Serenity we called law enforcement.”

The Associated Press contributed to this story.