Isabel Mercedes Celis Missing: Police expand search for 6-year-old to Mexico

(CBS/AP) TUCSON, Ariz. - A group of five people were captured on surveillance video leaving a club near the Celis family home around the time 6-year-old Isabel Celis disappeared.

Pictures: 6-year-old vanishes from Arizona home

ABC's Good Morning America reports one of the men captured in that footage could be a key witness in the case of the missing Ariz. girl as police start searching Mexico.

Three woman and two men were captured on camera just a block from Isabel's home. According to authorities, the group was walking away from the club at 1:30 a.m. in the direction of the house.

Tucson police say they've talked with at least three of five people captured on that video.

Lt. Fabian Pacheco says detectives wanted to talk with the group walking early in the morning to see if they saw anything unusual. Pacheco didn't say at a press briefing Sunday afternoon what the men and women told officers.

Dozens of tips are still being investigated as police try to find out what happened to the missing first-grader.

Meanwhile, the search for Isabel has widened, crossing over into Mexico. Saturday, U.S. marshals asked Mexican police for help checking hotels, bus terminals, and businesses in the town of Sonora, where the 6-year-old's photo is being circulated.

"The idea of having Mexico involved I think is a logical idea and a good idea at this point..."The idea that somebody crossed and picked up Isabel and then went back into Mexico is actually realistic," said former FBI agent Brad Garrett.

Isabel Celis was last seen around 11 p.m. on April 20 when she was getting ready for bed. She was reported missing by her father around 8 a.m. the next morning after he went to wake her up. According to police, the child was not in her room and a bedroom window was opened with the screen removed.

Although ABC News reports police have not ruled out Celis's parents as suspects, they have said the family has cooperated with police during the investigation.

Complete coverage of Isabel Mercedes Celis on Crimesider