Watch CBSN Live

Elizabeth Collins, Lyric Cook-Morrissey Update: Police seek killer of two Iowa cousins

Iowa cousins Elizabeth Collins (left), 8, and Lyric Cook (right), 10, disappeared on Friday, July 13, 2012. AP Photo/FBI

(CBS/AP) EVANSDALE, Iowa - A sheriff involved in the investigation of the apparent kidnapping and slaying of young Iowa cousins Lyric Cook and Elizabeth Collins says the discovery of their bodies represents a long-awaited break that could help find their killer.

PICTURES: Bodies found believed to be missing Iowa cousins

Black Hawk County Sheriff Tony Thompson said Friday that investigators are going to be deliberate in the case of 10-year-old Lyric and 8-year-old Elizabeth. The young girls disappeared in July while riding their bikes in Evansdale, Iowa.

Hunters found two bodies Wednesday believed to be the cousins in a secluded wildlife area 25 miles from Evansdale.

Thompson says it could take weeks for results of their autopsies to be released. Authorities are going to be "extremely meticulous" in their work because, he says, "We've got an opportunity to find a killer."

Black Hawk County sheriff's Capt. Rick Abben said Thursday at a news conference that investigators are "confident" the bodies are those of Lyric and Elizabeth, based on evidence found at the scene and a preliminary investigation. He noted that the bodies are small in stature and authorities "have no one else that's missing in this area."

Complete coverage of the case of the missing Iowa cousins on Crimesider