Authorities are delving into a fresh lead in the ongoing search for retired Air Force Major General William “Neil” McCasland, following the discovery of hiking boots thought to be his at his vacation residence, officials announced on Monday.

Investigators are currently determining whether these boots are linked to McCasland’s disappearance, a case that has now entered its third week without resolution.

At a press briefing on Monday, the Bernalillo County Sheriff’s Office revealed that there have been no verified sightings of the 68-year-old aerospace engineer. The Silver Alert, issued to help locate him, remains active.

McCasland was last observed departing his home in Albuquerque, New Mexico, on foot around 11 a.m. on February 27, according to authorities.

A photo, posted on Facebook by Susan McCasland Wilkerson, shows the missing retired General in his hiking gear, capturing an undated moment before his disappearance.

Officials reported that McCasland left behind his phone, glasses, and wearable technology at his home. Still, several personal belongings, including his wallet, a revolver, and its holster, are missing. Additionally, investigators mentioned on Monday that a red backpack is also unaccounted for.

Earlier that morning, McCasland was seen speaking with a repairman at his home around 9 to 10 a.m., according to authorities.

The repairman described McCasland as being in a “mental fog,” but investigators said there was no indication he was disoriented or confused, describing him instead as a “highly intelligent, highly capable” person.

“Out of an abundance of caution, we escalated the search to a Silver Alert with that information that was given to us early on,” a Bernalillo County Sheriff’s Office official said.

Authorities issued a Silver Alert for Ret. Maj. Gen. William Neil McCasland. (Bernalillo County Sheriff’s Office )

Authorities say McCasland vanished within roughly a one-hour window while his wife was out of the house for an appointment.

Search teams have also recovered a U.S. Air Force sweatshirt more than a mile from McCasland’s home, though investigators have not confirmed whether the item belonged to him.

McCasland is described as 5 feet, 11 inches tall with white hair and blue eyes and was last seen wearing a light green, button-up outdoor shirt with two chest pockets.

Officials believe he left his home on foot.

The retired general is known to be an avid outdoorsman who frequently hikes, runs and cycles in Albuquerque’s Northeast Heights and the nearby Sandia Foothills, where search crews have focused some of their efforts.

McCasland previously commanded Kirtland Air Force Base’s Phillips Research Site and Air Force Research Laboratory. (Kirtland Air Force Base )

Authorities said they have received dozens of tips and are urging residents to check home security video captured between Feb. 27 and Feb. 28, which investigators say is a critical window in the search.

The FBI joined the search effort on March 3, assisting local authorities as the investigation continues.

Investigators said they had not uncovered evidence of foul play, though officials have emphasized that no scenarios have been ruled out.

McCasland’s wife, Susan McCasland Wilkerson, has also pushed back on speculation tying his disappearance to his past military work.

“It is true that when Neil was in the Air Force, he had access to some highly classified programs and information,” she wrote in a Facebook post. “He retired from the AF almost 13 years ago and has had only very commonly held clearances since.”

Before retiring in 2013, McCasland commanded the Air Force Research Laboratory at Wright-Patterson Air Force Base in Ohio and holds a Ph.D. in aerospace engineering from the Massachusetts Institute of Technology.

Despite online speculation, his wife said he had no special knowledge about extraterrestrials or the Roswell incident.

Authorities are asking anyone with information about McCasland’s whereabouts to text BCSO to 847411 or contact the sheriff’s Missing Persons Unit at 505-468-7070.