TUCSON - The intense search for missing 6-year-old Isabel Celis continues, now in its 18th day.

Tuesday afternoon Tucson police held a briefing to update the public and media about the investigation.

There are no new leads that police can comment on. But they have received more than a thousand tips.

Right now, about 50 personnel are working the case, 20 detectives and 30 support staff.

The FBI and US Marshals are assisting too.

At Tuesday's news conference, Sgt. Maria Hawke said Isabel's disappearance is still classified as a possible abduction and they're investigating all possible scenarios.

"We've been examining every possibility. Whether it be extended family members, friends, people who have visited the neighborhood or regulars in the neighborhood. They have a very active social life outside of the home as well. So pretty much everyone they come into contact with has obviously been looked at," Sgt. Maria Hawke said Tuesday.

Sgt. Hawke says there's a multi step process detectives go through to eliminate possible suspects.

"There's a variety of hypotheticals that could cause somebody to be cleared. One example is if we can definitively prove that they were not in the city of Tucson at any time, during the time frame she potentially went missing," said Sgt. Hawke, "So that 11pm on Friday to 8am Saturday morning. If we can definitively prove that someone was not in town, it eliminates them from the suspicion of having taken her. But we then have to take the next step of eliminating them of having any knowledge of the incident."

So far, no one has been identified as a suspect and no one has been ruled out.