Carly "Charli" Scott, 27, of Maui vanished Sunday night after meeting with an ex-boyfriend who is the father of her unborn child, KGMB-TV, Honolulu reported.
Police were reported to have found Scott's burned-out sport utility vehicle Wednesday and her sister said she found clothes Thursday that Scott was wearing the night she disappeared, the TV station said.
The ex-boyfriend, Steven Capobianco, 24, was the last person known to have seen Scott alive. He told KGMB-TV they had broken up several years ago but "occasionally hooked up," including Sunday night.
Capobianco said the last he saw her was when they left for their separate homes in separate vehicles.
"And I'm pretty sure I saw her lights in my rear view the entire time. I'm absolutely certain I saw her headlights in my rear view mirror until I got to Twin Falls and then I started speeding up 'cause I drive a little faster than she does," Capobianco told the TV station.
He said he didn't learn she was missing until police arrived at his home Monday morning.
He said he had taken a polygraph test and police told him he failed.
"They didn't make me take it again," Capobianco said. "I'm honestly not convinced I failed, I think they might have just said that as a tactic, but I really don't know. I'm walking around right now without handcuffs on.
"They've just been questioning me. They haven't really told me anything. I mean, it's undeniable that I'm probably the prime suspect, so they're not going to tell me any details."