NEW YORK - Three construction supervisors and a subcontracting firm were indicted yesterday on manslaughter charges in the 2007 deaths of two firefighters at the former Deutsche Bank tower at ground zero, but the city was not charged.

The indictments cap a 16-month investigation that exposed numerous failures by city officials. Prosecutors said they interviewed more than 150 people, examined more than three million documents, and presented 80 witnesses to the grand jury.

"Everybody who could have screwed up, screwed up here," District Attorney Robert M. Morgenthau said of the fire.

Firefighters Robert Beddia and Joseph Graffagnino died of smoke inhalation in the tower, which was heavily damaged in the Sept. 11, 2001, attacks and was being demolished.

A construction worker's carelessly tossed cigarette caused the Aug. 18, 2007, fire, but the tragedy demonstrated a series of failures: The pipe supplying water to fire hoses was broken and the sprinklers didn't work, stairwells were blocked with plywood paneling meant to keep toxic debris in, no working elevator existed inside the building, and an air-pressure system created more smoke.

Investigators concluded that breakdowns by the Fire Department and Department of Buildings contributed to the conditions that led to the firefighters' deaths.

Jeffrey Melofchik, site safety manager for Bovis Lend Lease on the project, Mitchel Alvo, director of abatement for John Galt Corp., and Salvatore DePaola, a Galt foreman, pleaded not guilty in state Supreme Court to manslaughter, criminally negligent homicide, and reckless endangerment. Each could face up to 15 years in prison if convicted of second-degree manslaughter. The Galt company, which was dropped from the project after the fire, also was charged.

Prosecutors reached an agreement with the city and Bovis that requires them to institute major safety measures.

The building's demolition was put on hold for about a year because of the blaze.