NEW YORK - A cleaning woman who improbably vanished days ago from a Manhattan skyscraper bristling with security cameras was found dead yesterday, her body stuffed inside an air-conditioning duct on the 12th floor.

Police discovered the corpse, hidden in a utility room, just before 9 a.m. as they began searching the 26-story tower for the fourth straight day.

There was no official identification of the remains, but police spokesman Paul Browne said investigators presumed it to be the body of Eridania Rodriguez, 46, who had been missing since Tuesday night.

Authorities believe she was murdered but have not identified a suspect.

For days, workers at 2 Rector St. wondered how a missing-persons case such as this was possible in their building.

Like most office towers in the financial district, this one, a few hundred feet from the World Trade Center reconstruction site, got enhanced security after the 9/11 attacks.

Cameras cover every exit. Guards staff the lobby 24 hours a day. Visitors are photographed before they are allowed in. The streets outside are patrolled by a high concentration of police officers. Nearly every block in Lower Manhattan is covered by security video.

Cameras recorded Rodriguez when she turned up for work at 5 p.m. Tuesday, and again as she moved around the building, but they never showed her leave.

Rodriguez, who was born in the Dominican Republic, had lived in Manhattan for decades. She was married, had several children, and was the sister of a top-ranked professional bodybuilder, Victor Martinez.