Handlers and their specially trained dogs plied the waters of the Colorado River in boats in a so-far futile search for two Yuma children missing since their mother was found beaten to death a week ago.

The Utah searchers joined area crews shortly after arriving Wednesday, then spent Thursday in the same fruitless endeavor without finding LeCresha Kirklin, 9 months, and Shemeash Gunnell, 5.Their mother, Valerie Lorraine Gunnell, 26, was found dead in her apartment after police received an anonymous telephone tip.

Police reported the caller also said the girls might have been thrown into the river. Authorities say they fear the children are dead.

Alvie Copeland Kiles, 27, of Yuma, was charged Tuesday with first-degree murder and was ordered held without bond in Yuma County Jail. Kale Lamont Johnson, also 27 and of Yuma, was being held in the county jail for parole violation from a 1986 assault conviction.

Yuma police said Kiles resided with Gunnell.

Police Capt. Richard C. Leffler said the mother's slaying and the apparent likelihood that the children also had been killed upset the community. Authorities said 15 to 25 friends and family members walk the banks of the river each day looking for the children.

Lindsey Richards, 28, Gunnell's cousin, said Gunnell went to school in Yuma, where she had many friends, and had relatives in Tucson. She was unemployed when she was killed but had worked in a Tucson yarn mill.

"We're very concerned about getting the kids back - dead or alive," Richards said.

Leffler said that "when you have two young kids missing like this, it tends to make police officers work a little hard to solve it."

The dogs, trained to detect gases from decomposing bodies, were accompanied by handlers Tom Shirley and Jed Abbott of Sandy, Utah, and Rocky Mountain Rescue Inc., a volunteer group that conducts search-and-rescue missions throughout the West.

Leffler said the dogs could detect such an odor originating under water or from under the surface of land.