Searchers on foot and horseback combed 455 acres of the El Sereno hills while others flew overhead in a helicopter and dog handlers deployed bloodhounds.
The apparent victim, described as 13 or older - and possibly a small woman - was reported kidnapped Monday night near a recreation center during an argument with a young man who may be between 18 and 20, police said. Sketches of both the girl and the man were released late Tuesday.
"That argument escalated to the point where the male struck the female at least once in the face and then began to drag her up into the brush area by the hair," police Lt. Andy Neiman said.
Witnesses followed and saw the man begin to remove some of the girl's clothing, he said.
Police Chief Charlie Beck said the only evidence officers had found in the search, which was 90 percent complete Tuesday afternoon, were some leggings and tennis shoes.
"My hope is that this was a dispute that was resolved in some way, but we have to treat everything like it's the real deal," Beck said at a news conference.
No reports of a missing girl had been filed, but the witnesses seemed credible, police said.