Investigators have completed four days of forensic digs in Virginia in their search for two young sisters who disappeared in 1975.
Authorities said Monday they hope to find human remains.
Multiple agencies, including the FBI and police from both Virginia and Maryland, have been searching on Taylor Mountain in Bedford County, Virginia, in an attempt to locate Katherine and Sheila Lyon. The girls were 10 and 12 years old when they disappeared March 25, 1975, after visiting a shopping center in Wheaton, Maryland.
"Investigators are pleased with the progression of the search for the truth concerning the abduction and murder of the Lyon sisters," the Bedford County Sheriff's Office said in a release Thursday. "This progression is the direct result of careful, methodical and thorough work this week."
Bedford Co. Sheriff Mike Brown and Commonwealth's Attorney Randy C. Krantz thanked the members of the FBI Evidence Recovery Team "for their tireless and dedicated work to bring Sheila and Katie Lyon home."
Authorities did not specify whether they located anything in the search.
An FBI evidence recovery team and a Radford University forensic pathologist joined state and local investigators, Bedford County Sheriff Mike Brown said Monday.
NEW: Searchers hope to find human remains in #LyonSisters search on Taylor Mountain.— Richard Jordan (@JordanNBCDC) January 12, 2015
During a news conference Monday with police from Maryland and Virginia, Brown declined to say what new evidence led investigators to the location. Asked if it appears human remains will be found, Brown said, "We would hope so."
The search is expected to take two days, but the weather is not cooperating, authorities said Monday.
Investigators have been searching a property in Bedford County, Virginia, which was once owned by the family of 57-year-old Lloyd Lee Welch Jr., also known as Michael Welch. Welch, a child sex offender in a Delaware prison, was named a person of interest in February.
Welch is originally from the D.C. area and was known to hitchhike throughout the region. Between the 1970s and the mid-1990s, he traveled extensively through the United States while working for a carnival company with his girlfriend, Helen Craver, police said.
Welch was charged with raping juveniles in Virginia and South Carolina. He was also arrested in a burglary not far from Wheaton Plaza.
His uncle, Richard Allen Welch Sr. of Hyattsville, Maryland, was named a person of interest in October. Authorities believe he was a security guard in the Wheaton area at the time of the sisters' disappearance and that the family owned property in Bedford County, said Montgomery County Police Chief Russ Hamill last October.
Neither man has been charged in the Lyon case, but Richard Welch's wife, Patricia Jean Welch of Hyattsville, Maryland, was indicted last month on a charge of lying to a grand jury.
Bedford County Commonwealth's Attorney Randy Krantz urged any residents with information about the case to come forward.
"Our mission focus is to bring these children home if at all possible," Krantz said.
Late last year, the Bedford County Sheriff's Office requested the public's help in identifying a late 1960s or early 1970s vintage station wagon that was "associated with the crime."
No further description of the station wagon was given, but the sheriff's office said it "may have been hidden in, or removed from, a barn, shed or outbuilding."
On March 25, 1975, the Lyon sisters had planned a day at Wheaton Plaza, now known as Westfield Wheaton Mall. They were on spring break, and wanted to get pizza for lunch and see the Easter decorations at the shopping center.
With less than $4, they left their home in Kensington, Maryland, and walked the half-mile or so to Wheaton Plaza.
There, a friend saw the girls outside the Orange Bowl restaurant with an older man who had a tape recorder and a briefcase, according to news and missing persons reports.
The girls were later spotted walking home, but by their 4 p.m. curfew, they hadn't arrived. By 7 p.m. that night, police had been called.
Later, a composite sketch was distributed of the man who seen talking to them. Tips flowed in, but to no avail.
Sheila and Katherine were never seen again.