Law enforcement officials believe they can capture accused cop-killer Eric Frein by depriving him of food and starving him out of his heavily-wooded hiding spot.

The search for Frein entered its fourth week Saturday. The 31-year-old survivalist is charged with killing a Pennsylvania State Trooper and wounding another in a late-night ambush at a rural state police barracks in Pike County Sept. 12.

Police leading the manhunt said Friday they seized tuna fish, instant noodles and other food at a campsite recently used by Frein in the northeastern Pennsylvania woods. A search of the campsite had also turned up two pipe bombs, ammunition, clothing and even soiled diapers.

The Allentown Morning Call, in a story Friday quoted Lt. Col. George Bivens as saying that police are seizing Frein's food and maybe that's how they'll catch him.

Bivens believes cutting off Frein's supplies will force the fugitive to forage for food in trash bins or dumpsters or to break into cabins to feed himself.

"Because we continue to push Frein, and to seize the items he needs to survive, we believe he will be forced to search for food and shelters in other locations," the colonel said during an update Friday on the manhunt three weeks after the shooting that killed Cpl. Bryon Dickson and seriously wounded Trooper Alex Douglass.

Hundreds of law enforcement officials have been searching for Frein in the woods around his parent's home in Canadensis. Police have spoken with Frein's family about making a public appeal for his surrender, but no decision has been made, Bivens said.

Meanwhile, DNA testing on those recovered soiled diapers was inconclusive, the FBI said Friday.

The diapers had been exposed to the elements, so "you can't say one way or the other" whether Frein wore them, Edward Hanko, special agent in charge of the Philadelphia FBI office, said in a phone interview.

The diapers might have belonged to Frein, but the testing didn't confirm it or rule it out, Hanko said.

Bivens said the diapers are still considered evidence in the case. He declined further comment.

The manhunt is concentrated on a heavily forested area in the Pocono Mountains. Authorities believe they have spotted Frein from a distance, but the rough terrain made it impossible to get to him. The last sighting deemed highly credible came earlier in the week, Bivens said.

Frein has been described as an anti-law enforcement survivalist and expert marksman at home in the woods. He is considered armed and dangerous.

The Associated Press contributed to this report