Authorities in Houston are searching for a 4-year-old girl who was reported missing Saturday night by her stepfather.

Police say Maleah Davis may have been abducted by three men in a 2010 blue Chevrolet pickup, although authorities say their investigation is in its early stages. Detectives with the Houston Police Department are relying almost entirely on information provided by the girl’s stepfather, Darion Vence, who says he was ambushed by the men while driving to the airport Friday night with Maleah and his 2-year-old son. All three were abducted, Vence told police. He and the boy were left on the side of a highway nearly 24 hours later, Vence said, but Maleah was missing.

Vence told authorities he does not recall much of what happened between Friday night and Saturday night because he had been knocked unconscious.

Authorities said they are concerned for Maleah’s safety — not only because she may be in the hands of kidnappers, but also because she has endured significant health problems, including multiple brain surgeries, the most recent of which she underwent about a month ago.

She had been ill in the days leading up to her disappearance, Sgt. Mark Holbrook said at a news conference Sunday.

Holbrook acknowledged to reporters that Vence’s version of events includes significant gaps and a lack of detail, which is why the police department is calling on the public for help to inform the timeline.

“We’d love for the public to help us so we can fill in the blanks in this story,” Holbrook said. “I realize there’s a lot of blanks in that story.”

According to Vence, he was driving to George Bush Intercontinental Airport around 9 p.m. Friday to pick up the children’s mother, who was traveling home from Massachusetts. Vence said he heard a popping noise and pulled over to make sure he didn’t have a flat tire.

A blue pickup then pulled up behind them, Vence told authorities, and two men got out of the truck. One made comments about Maleah, Vence said, including that she looked nice and sweet. The other hit him in the head, Vence told authorities, knocking him unconscious.

At some point, Vence said, he awoke in the back of the truck with both children. There were three other men in the vehicle. Vence then said he lost consciousness again. When he woke up the second time, he said it was about 6 p.m. Saturday and he and the 2-year-old boy were on Highway 2. Maleah was not with them.

Vence told authorities he tried to flag down help on the highway, but nobody would stop. He and the boy then walked to Houston Methodist Sugar Land Hospital, Vence said. They arrived around 10 or 11 p.m., Holbrook said during the news conference. They reported Maleah missing at the hospital.

Maleah’s mother, whom authorities have not identified, did not report Vence or the children missing, Holbrook said during the news conference. She arranged for other family members to pick her up from the airport, authorities said.

Holbrook told reporters that Vence is at home with family. He does not have a criminal record, Holbrook said. Maleah’s biological father, who also lives in the Houston area, has been contacted by authorities and is being cooperative, Holbrook said.

At the news conference, authorities shared a photo of the type of truck Vence described: a 2010 blue Chevrolet crew cab pickup. They also shared a photo of the car Vence was driving when the alleged abduction occurred, a silver 2011 Nissan Altima with Texas paper tags 330-92G9. The Nissan belongs to Maleah’s mother, authorities said. She had just purchased it at a dealership.

Traffic cameras captured a photo of the Nissan driving through an intersection Saturday afternoon. It has not been seen since.

Authorities have not found any surveillance footage or witness accounts that corroborate Vence’s version of events.

“Darion doesn’t remember a 24-hour period of his life,” Holbrook said. “If somebody saw him, if maybe he was walking around in a daze, I’d love to know anything about that.”

When reporters at the news conference expressed skepticism about the veracity of Vence’s memories, Holbrook said authorities were relying on the public to aid the investigation.

“We’re hoping, the purpose of the press conference is to figure out what really is true, what really happened,” Holbrook said. “We don’t know. I just don’t know. And I don’t want to speculate.”

A small search party handed out 100 missing-person posters in a park in Sugar Land, near where Maleah allegedly disappeared, CNN affiliate KPRC reported. The group of five women, friends of Maleah’s mother, resumed their efforts Monday and were joined by Texas EquuSearch.

“She’s a spunky little thing, you know, and she’s beautiful,” Amber Fannin, a family friend helping with the search, told KPRC. “She has a beautiful energy and we just want to find her at this point.”

Authorities issued an Amber alert that included a description of the outfit Maleah was wearing when she disappeared: a pink bow in her hair, a light-blue zip jacket, blue jeans and sneakers that are gray, white and pink.

Police encourage anyone with information to contact Houston Police Department Homicide at 713-308-3600 or Houston Crime Stoppers at 713-222-TIPS.