Police are digging behind a shed at a North Dartmouth home owned by the family of the man suspected of killing a Saxonburg, Pennsylvania police chief in 1980.

It was revealed in June that a secret room in the house, where suspected killer Donald Eugene Webb's family has lived for two decades, was discovered by the FBI as much as a year ago, but made public as part of the slain chief’s family’s quest for justice.

Webb, described by the FBI as a career criminal specializing in jewel theft, is accused of gunning down Saxonburg Police Chief Gregory Adams during a routine traffic stop on December 4, 1980. The FBI believes Webb was in Pennsylvania that day casing a jewelry store to rob. It is believed that he returned to New England after the murder. His getaway car was discovered in a Rhode Island hotel parking lot later that month.

Kristen Setera of the FBI's Boston office confirmed that the FBI, Pennsylvania State Police, and Massachusetts State Police assigned to Attorney General Maura Healey's office are conducting a search as part of the investigation.

"As part of our ongoing efforts to locate longtime fugitive Donald Eugene Webb, an evidentiary search is currently underway," Setera said. "Due to the ongoing investigation, no further comment will be made at this time."

Adams' family filed a lawsuit in June, after learning of the secret room, that the family's attorney, Thomas King III, said was an attempt to secure the cooperation of Lillian Webb and her son, Stanley. The family believes the pair has information about Donald Webb's whereabouts.

The room contained a cane – a significant discovery because it is believed Donald Webb was shot in the leg during the altercation that claimed Adams’ life. If he is still alive, Webb would be 85 years old.

Reached Thursday afternoon, King declined to comment.

Observed at the home on Thursday were the FBI, Massachusetts State Police, Saxonburg Police, Dartmouth Police, Bristol County District Attorney Thomas Quinn, and a police dog.

Saxonburg Police Chief Joseph Beachem wouldn't comment on his role in the investigation, but did say that making the drive from Pennsylvania was a must.

“I am here because obviously there’s some hope in the case and to support the efforts of the FBI, Massachusetts State Police, and the Pennsylvania State Police," he said. “I know that it’s been an open question for so long that it’s on a lot of people’s minds, including everybody in our department.”

Digging could be heard at the home for hours, beginning in the early afternoon. Police activity continued into the early evening, even in thunder, lightning, and rain. A tarp was later stretched above the dig site and work lights illuminated the area.

At one point, a reporter asked if the rain was holding officers back.

A State Police officer noted that investigators were in it for the long haul.

Neighbor Maria Medeiros said she's lived next door for 35 years and never saw anything out of the ordinary.

"If I see [Lillian Webb] in the street I can recognize her face, but I never heard anything," Medeiros said. "I never saw a man over here."

Raymond Rapoza, who has lived in a house on the corner of the street since 1988, said he's never encountered the family, either. But he has seen a lot of activity.

"This is like the fourth time already I've seen all the cops and detectives here," he said.

Jacob Dias, 18, who lives across the street, said he oftentimes gets home around 2 or 3 in the morning on weekends, and has seen Lillian Webb leaving her home at that time.

"I've seen her three or four times" leaving that early in the morning, he explained.

Medeiros observed the police presence on Thursday and heard the digging in the yard.

"I'm not afraid," she noted. "They're doing their job."

Kevin Ponte, an electrician working nearby, stopped by the street later in the afternoon after hearing of the police activity.

Ponte, a Dartmouth resident, said he met Stanley Webb about a month ago while doing work for him at The Donut Factory in New Bedford.

"Great guy. Very helpful. Very nice guy. Honest. I liked him," Ponte said.

He called the situation "shocking."

"I think it's pretty crazy. It's shocking, it really is," he said. "I haven't seen much, just waiting to see what the outcome is. I guess they're shoveling back there near some sheds. I guess they have some info that the body is there in the backyard."

Dartmouth Week has not been able to confirm what authorities are looking for in the yard.

The FBI is offering a $100,000 reward for information leading to Webb’s whereabouts, or the location of his remains if he is no longer alive. The agency issued never-before-released photos of him in mid-June with the hope that the photos would generate new leads on the cold case.