Authorities are conducting a new search on a Virginia mountain for the remains of two Maryland sisters who disappeared in 1975.

The Bedford County Sheriff's Office said Monday that additional leads prompted another dig on Taylor's Mountain, but officials didn't provide details. The operation is expected to take several days.

The sheriff's office, the Virginia State Police and the Montgomery Police Department in Maryland are conducting the search for the remains of 10-year-old Katherine Lyon and 12-year-old Sheila Lyon. The sisters disappeared after walking to a shopping mall in Wheaton, Maryland.

An earlier dig was conducted on the mountain in January.

Authorities have named Richard Allen Welch Sr. and his nephew, Lloyd Lee Welch, as persons of interest in the case. Neither man has been charged.