ROCKERVILLE, S.D. (AP) — The search for a 9-year-old girl who ran away from a children’s home in South Dakota has involved more than 1,000 people who have logged more than 4,300 miles since she disappeared in February, according to sheriff’s officials.

Serenity Dennard left the Black Hills Children’s Home near Rockerville on the cold and snowy day of Feb. 3 in a mountainous and forested area in the southwestern part of the state.

“It’s frustrating to people that we haven’t found her,” Pennington County Sheriff Kevin Thom said. “It’s frustrating to us that we haven’t found her. But that doesn’t mean we’re going to stop looking.”

Another search involving about 35 people from multiple local and regional agencies on Thursday combed the area where Serenity was last seen, the Rapid City Journal reported. It’s the latest of numerous official searches that have also included 91 dogs and their handlers and seven aircraft.

Investigators have chased 195 leads in 15 states, conducted 440 interviews or contacts and executed six search warrants, according to the sheriff’s office.

Additionally, the sheriff’s office has shared information on social media. The case on the National Center for Missing and Exploited Children website has resulted in millions of views, according to web traffic monitored by the sheriff’s office.

The search changed from a rescue to a recovery effort not long after Serenity went missing. Authorities said Serenity likely wouldn’t have survived if she was outside in subzero temperatures.