Holloway disappeared on the last night of a trip to Aruba to celebrate her graduation from high school. Four days later, the Alabama teenager is still missing, despite an extensive search of the Dutch Caribbean island.
"Honestly, at the beginning, we were hopeful the girl would come back," said police Superintendent Jan van der Straaten. "Today, we are more and more thinking about the possibility of a crime."
On the island remarkable for its absence of violent crime, hundreds of residents and tourists posted fliers to help the hunt. FBI agents helped the Dutch military and Aruba police scour outlying scrubland with helicopters and all-terrain vehicles but found no trace of the 18-year-old.
"Everybody has been quite supportive," the teenager's mother, Beth Holloway Twitty, told The Associated Press. "I am not leaving. I am going to have Natalee with me."
Holloway came to Aruba for a five-day excursion with 124 seniors and 40 chaperons from Mountain Brook High School, near Birmingham, Ala. She was last seen around 2 a.m. Monday, Attorney General Caren Janssen said Thursday.
Police discount the possibility she left the island, because they found her passport in her hotel room, van der Straaten said.
Hopes were lifted briefly just before midnight Thursday when a news photographer said he had seen Holloway on the west side of the island. Police rushed to the scene but found an island girl who fit the description but had brown hair, not Holloway's long blond tresses.
Dressed in the same blue-and-green striped, low-cut blouse and denim miniskirt that she wore at the beach earlier in the day, Holloway spent Sunday evening partying at Carlos 'n Charlie's, a popular restaurant and dance spot where tourists and locals meet in the capital, Oranjestad.
Friends saw her getting into a vehicle outside the nightclub. She did not show up to catch her flight Monday. Her stepmother, Robin Holloway, said Natalee was last seen with a local resident who claimed to be a foreign exchange student.
Police questioned and released three Aruban students who said they dropped Holloway off early Monday at the Holiday Inn where she had been staying, about three miles from Oranjestad, said police assistant inspector Jules Sambo.
"We don't have any indication as to if she is alive," Sambo said. "The whole population is aware that she is missing. The police are doing everything to find her."
Several family members arrived the day after she disappeared. Her mother and her father, David Holloway of Meridian, Miss., went on television Thursday night to appeal to residents for information.
"We want everybody, as many people as we can to pray for Natalie," said Francis Ellen Bird, who was on the trip with Natalee. "I talked to her mom today she said she could feel that everybody was praying for her."
The island of 72,000 off the coast of Venezuela has a reputation of being all but free of crime for tourists.
There was one murder and six rapes last year and two murders and three rapes this year. But all the rapes were committed by local men against local women. The two murders involved drug addicts who died in knife fights.
"Aruba is a happy island and a safe island," said Janssen, the attorney general. "We're looking everywhere."