An Amber Alert was issued Monday for a pregnant 16-year-old who was allegedly kidnapped at knifepoint from her mother's California home by her abusive older boyfriend, according to local media reports.

Ashlee Crocitto is four months pregnant and was reportedly taken at about 8:45 a.m. Saturday by 20-year-old Carlos Antonio, Chula Vista, Calif., police told the local TV news.

Her tearful mother told FOX News on Monday that the alleged abduction wasn't a plot by her daughter to run away with Antonio and said Ashlee is a totally different person when she's with him.

Police concurred, saying they are operating under the assumption that the kidnapping was real.

"There doesn't appear to be any doubt that it was not voluntary," Bernard Gonzales, a public information officer with the Chula Vista Police Department, told FOXNews.com on Monday.

"This individual was lying in wait and forced her into the vehicle at knifepoint. There's always a possibility that it was an act, but we don't operate under assumptions. We take it seriously."

Gonzales said Crocitto was apparently pregnant with Antonio's child and at some point the pair had been girlfriend and boyfriend, but he couldn't say whether the couple was still together.

Various local media reports said the teen had recently broken up with Antonio because he was abusive.

Crocitto has apparently called home a few times since Saturday to tell her mom that she's OK, but police and her family are still worried about her safety.

Gonzales said that Crocitto and Antonio might be in a bluish-green 1999 Hyundai Accent with California license plate number 4EPA103, and Antonio had initially spoken of fleeing to Mexico.

"We know that the suspect had indicated he wanted to go to Mexico," he told FOXNews.com. "We got the word out. We don't believe there was any attempt by him to get across the border."

Anyone who has any information about the case is asked to call Chula Vista police at (619) 691-5151.

Click here for more on this story from KGTV San Diego.

FOX News' Catherine Donaldson-Evans contributed to this report.