Isabel Celis search: Hunt for 6-year-old girl moves into Mexico

Arizona investigators hunting for missing tot Isabel Celis spoke with a man captured on surveillance camera near the girl's house on the night she disappeared, police said.

The unidentified man was one of five people filmed walking near the Celi's home at 1:30 a.m. after leaving a club on April 21.

Authorities didn't reveal what the potential witness told them or whether he had any information that put them closer to finding the 6-year-old, ABC News reported.

News of the video came as authorities announced the desperate hunt had crossed into Mexico.

Tucson police spokesman Lt. Fabian Pacheco told reporters on Saturday that Mexican officials in the northern state of Sonora were searching hotels, bus terminals and businesses, and circulating the girl's photo.

Pacheco also called for patience, saying that investigators were looking "at all possible scenarios" — though they have ruled out Isabel leaving on her own.

"We understand that some folks might feel frustration. Eight days, believe me, we feel it as well," he said, according to The Associated Press.

"This isn't 'CSI Tucson' where we're going to solve this in an hour. It's going to take us a while and we need that patience," he said.

Former FBI agent Brad Garrett told ABC News it was "a good idea" to get Mexican police involved.

"The idea that somebody crossed and picked up Isabel and then went back into Mexico is actually realistic," Garrett said.

Isabel was reported missing by her father, Sergio, at around 8 a.m. on April 21 after he went to wake her up and found her bedroom empty.

A window to the room was open and a screen was removed, police said.

Last week, search dogs picked up on something suspicious in the home and the family was evacuated from the house.

Investigators later searched several homes in the Celis neighborhood and interviewed around 15 people who are on the state's sex offender registry.

Sergio and Becky Celis have offered $6,000 for any information about her whereabouts.

"Just please, please, to the person or persons who have Isabel, tell us what you want. We will do anything for her," Sergio Celis said in a tearful plea last week. "We're looking for you, Isa."