GREELEY, Colo. -- Police confirmed Thursday that a body found in an irrigation ditch in northern Colorado is that of a missing 12-year-old girl who was last seen walking to a friend's house for a birthday party.

Greeley Police Chief Jerry Garner said the body recovered Wednesday is that of Kayleah Wilson, of Greeley, and that the coroner's office ruled the death was a homicide. He said police know the "manner and cause" of death but he declined to provided details. No one has been arrested.

The decomposed body had been in the irrigation ditch "for some time" in an area that had been searched twice, Garner said. Greeley is about 60 miles northeast of Denver.

The ditch is about a half-mile from the sixth-grader's home. A worker checking the ditch after heavy rain found the body in about three feet of water, Sgt. Joe Tymkovich said.

Wilson's disappearance on March 28 spawned repeated searches by police, Greeley residents and the FBI. Authorities said they pursued more than 300 leads and knocked on the doors of about 1,000 homes.

No one has been ruled out as a suspect, but investigators have nothing that points to family members, Garner said.

Tymkovich said police are looking at a range of individuals who had the time and opportunity to kill Kayleah and don't have good alibis.

"The investigation has really turned a corner with the discovery of this body," Tymkovich said.

Authorities received additional tips on the case after the body was recovered, and police will vigorously press the investigation, he vowed.

"We don't give up on cases like this," Garner said.

Police met with Wilson's mother, April Wilson, before the public announcement, the chief said.

"She's upset as you would expect," he said.

Family friend Cindy Rogers said finding out about Kayleah "sure is devastating."

"But now I'm glad that it's her because now the community can lay her to rest," Rogers said. "She can go home to where she belongs."

Rogers called Kayleah "a very sweet, quiet young girl."

"She loved to laugh. She had a really great personality. She's going to be missed," Rogers said.

After the police news conference, a dozen or so people showed up at a makeshift memorial of flowers and teddy bears along the grassy banks of the irrigation ditch where Kayleah's body was found. About 150 people held a vigil in the same place Wednesday night.

Authorities had stressed they didn't know if Kayleah Wilson had run away or was abducted and did not issue an Amber Alert, which notifies the public about a possible child abduction through text messages, phone calls, radio and television broadcasts and highway signs.

Authorities said criteria for an alert include information that a child may be in danger or if a suspect has been identified. The criteria ensure that the public won't ignore alerts because they are not broadcast often.

In April, as leads from the public dwindled, authorities increased the reward for information about Wilson to $20,000. Investigators also described behavior that might point to a possible abductor. They urged people to watch for someone who had missed work, had unexplained injuries or shown an unexpected or sudden interest in the case.