The Latest on the rescue of three adults at an inactive coal mine in West Virginia (all times local):

5 p.m.

A West Virginia sheriff says he plans to conduct a thorough investigation into four adults who went into an inactive coal mine.

Raleigh County Sheriff Scott Van Meter said Thursday the criminal investigation will focus on why the adults were in the Elk Run Coal's Rock House Powellton mine near Clear Creek and find out "what happened."

Three adults were rescued Wednesday night after spending four days inside the underground mine. A fourth adult had walked out of the mine on Monday. An abandoned ATV the four were believed to be riding had been found near the mine entrance.

A father of one of the rescued adults had indicated his daughter went into the mine to look for copper. Van Meter hadn't seen those comments but says people trying to steal copper from West Virginia mines is "nothing new."

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2:30 p.m.

A prosecutor says a sheriff's office is conducting a criminal investigation into four adults who went into an underground coal mine in West Virginia.

Raleigh County Prosecutor Kristen Keller says she began discussing potential charges with the Raleigh County sheriff's office when the search began Sunday.

One adult emerged from Elk Run Coal's Rock House Powellton mine near Clear Creek on Monday. Three others were rescued inside the mine Wednesday night. An abandoned ATV the four were believed to be riding was found near the entrance of the inactive mine.

The father of one of those rescued has said his daughter went into the mine in search of copper.

Sheriff Scott Van Meter didn't immediately return a phone message seeking comment on the investigation.

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10:45 a.m.

One of three adults rescued after four days in an inactive coal mine in West Virginia says he learned a valuable lesson.

The faces of Cody Beverly and the others were covered in soot as they emerged from an ambulance and were reunited with loved ones Wednesday night before being taken to a hospital for treatment.

Beverly says the four-day experience "was terrible."

Beverly thanked the crews that had been searching for the group since Sunday. He told NBC News , "This is the biggest lesson I've ever learned in my life. This is a life-changing experience for me."

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9:35 a.m.

The father of a woman found alive after spending days in an underground coal mine in West Virginia says his daughter went into the mine in search of copper.

Randall Williams told CBS News that people in the region do "whatever they can do to make money if they ain't got a job." It's not uncommon for people in the area to enter abandoned mines in search of copper to sell.

His daughter, Kayla Williams, and two others, Erica Treadway and Cody Beverly, were found Wednesday inside Elk Run Coal's Rock House Powellton mine near Clear Creek. TV news video later showed them emerging from an ambulance and walking into a hospital escorted by law officers and rescue workers. They had been reported missing Saturday.

The mine was described as nonoperational.