The workers told Guy Jessop, who met them at the gate, they were "looking for more children" but he refused to let them enter without a search warrant.
News of the visit reached the Tom Green County Courthouse, where the third day of status hearings for about 450 FLDS children was under way. Several FLDS spokesmen - and media - made a mad dash to the ranch, whose residents are members of the Fundamentalist Church of Jesus Christ of Latter Day Saints.
CPS officials spoke with FLDS member Willie Jessop after being rebuffed and were told he would allow them on the ranch, according to spokeswoman Marleigh Meisner.
Investigators returned to the ranch at about 6 p.m. but Willie Jessop met them at the gate and turned them away, she said.
Willie Jessop said ranch residents would allow authorities to investigate any legitimate claims of abuse. "If they have an honest complaint, we'll be honest, but we were lied to," he said, noting that authorities have never produced the teenage girl whose allegations of abuse led the state to remove all children from the ranch in April.
Jessop said he does not know whether there are children at the 1,700-acre property, which includes 19 separate residential buildings. If there are, they would have arrived with parents who came to comfort relatives in the wake of the April raid, he said.
Meisner said she did not know what action CPS might pursue next in its effort to search the ranch.
Meisner would not comment on the new information the agency has received. She said CPS, which does not conduct criminal investigations, never uses search warrants.
"These attempts are part of our ongoing investigation," she said.
A search warrant was used when Texas Rangers and CPS workers raided the ranch in April.
Rod Parker, a sect spokesman, said CPS officials told Willie Jessop that an informant claimed there are five children at the ranch, including a boy who has Down syndrome.
A 5-year-old boy with Down syndrome was among the children previously taken from the ranch, though it is not clear if CPS officials are looking for a different boy with that same condition.
Meisner would not confirm any information about children CPS believes may be at the ranch or say when the agency received the information.
The timing of the account was unclear and it could be weeks old, Parker said.
This marks the first time investigators have returned to the ranch since completing a raid and weeklong search that began April 3. CPS said it found evidence of a pattern of abuse - such as sex with underage girls - that justified removal of all the sect's children.
* THE ASSOCIATED PRESS contributed to this story.
Texas officials raided the YFZ Ranch beginning April 3 after a San Angelo shelter said it had been contacted by a caller claiming to be Sarah Jessop, a 16-year-old abused by her polygamous husband, Dale Barlow.
Those calls were traced to a Colorado woman with a history of making false calls for help. In a further sign the calls were a hoax, the child welfare case involving Jessop and Barlow was dismissed Monday.
But child welfare officials say once they were on the ranch, they found evidence of a pattern of abuse that justified removal of all children. The ranch is home to members of the Fundamentalist Church of Jesus Christ of Latter Day Saints, a polygamous sect traditionally based on the Utah-Arizona border.