undreds of patients released from state psychiatric hospitals in New York in recent years are being locked away on isolated floors of nursing homes, where they are barred from going outside on their own, have almost no contact with others and have little ability to contest their confinement, according to interviews with workers and experts and visits to the homes.

The Pataki administration approved the creation of the special units for the mentally ill in 1996, but has otherwise left them unregulated. The nursing homes generally lack mental health expertise, and have not sought licenses to operate locked floors.

As a result, some experts said, the administration was allowing the homes to violate state regulations governing the care of the mentally ill and in the process was depriving them of their civil rights.

The conditions in the locked units, which the administration authorized with no public notice, were uncovered in a four-month investigation by The New York Times. The investigation was based on multiple visits to the homes - many are in New York City - as well as more than 50 interviews with residents, relatives, workers and officials.

The units are in nursing homes that mainly care for the elderly. They are not part of the separate system of adult homes for the mentally ill, which were the focus of a series of articles in The Times earlier this year that detailed extensive neglect and malfeasance.

The units are just the latest development in the troubled evolution of New York's mental health network over the last half-century. As the state continues to empty out its costly psychiatric hospitals, it appears to be moving even further from what it says had been a fundamental goal: helping the mentally ill gain independence and self-sufficiency to live within a community.

The investigation of the nursing home units shows that the mentally ill residents - many in their 30's and 40's and physically healthy - often receive little in the way of rehabilitative therapy and are chiefly left to wander the halls or languish in their rooms. The residents are not violent and have not been involuntarily committed by a court.

Yet on the fourth floor of the New Surfside nursing home in Far Rockaway, Queens, about 50 mentally ill people are prevented from going outside by locked elevators and fire doors with alarms. Residents at the nearby Haven Manor nursing home are outfitted with electronic bracelets that trigger an alarm should they try to leave. And at the Woodmere nursing home in Nassau County, residents have broken windows in a desperate bid for freedom, workers said.

Gov. George E. Pataki would not comment for this article. Administration officials and a main operator of the homes disputed that the floors are technically locked. They said the units are merely secured, and thus do not legally require a special license. The officials said the units provided quality care and did not confine residents against their will.

Visits to the homes and interviews with workers and residents like Leonard Holloway indicated otherwise. Mr. Holloway, who is 48 and has schizophrenia, was not allowed outside Haven Manor until late last month, three months after arriving at the home and only after being visited by a reporter. ``You feel like you're in a - like you're a prisoner in here,'' said Mr. Holloway, once a clerk at the main branch of the New York Public Library.

Tacked on the wall over his bed is evidence of what he has accomplished during his stay: three children's jigsaw puzzles that he put together during recreation time.

Many mental health advocates and lawyers were unaware of the units and voiced dismay when told of the restrictions.

``I have never heard of this type of facility in the 12-plus years that I have been doing this,'' said Tim Clune, managing attorney for Disability Advocates, a nonprofit legal office in Albany. ``I am very surprised that this exists, and that the state would allow this to exist. This is de facto involuntary commitment. These people's civil rights are being violated.''

Administration officials said they did not know exactly how many units were operating. The State Office of Mental Health estimated that at least a dozen existed, suggesting that as many as 1,000 mentally ill people lived in them. Yet the office, which was responsible for discharging the patients from the state psychiatric hospitals to the units, has chosen not to take a role in overseeing them or ensuring that residents receive proper care.

The administration's chief nursing home regulators, Dr. Antonia C. Novello, the state health commissioner, and Wayne Osten, a senior health official, said the units were appropriate and had been examined by officials during routine inspections of the homes. They said the units, which the department refers to as ``neurobiological units,'' did not need additional regulations.

``The residents can leave the units if they want,'' Mr. Osten said. ``From our standpoint, there are means of egress for the residents.''

Mr. Osten said it would be incorrect to call the units locked, explaining that while elevators were often ``keyed,'' as he described them, the fire doors were only alarmed.

But workers said in interviews that residents are told that under no circumstances are they permitted outside on their own. The workers said the floors were confined to prevent the mentally ill residents from mixing with elderly residents on other floors. The restrictions also allow the homes to avoid hiring more staff to keep track of the mentally ill residents, the workers said.

An aide to Benjamin Landa, who is a partner in four homes with units, said state officials knew about the restrictions imposed on residents, adding that health and mental health officials had repeatedly visited the homes. The aide, Frank Iannucci, said the residents agreed to the conditions before they were admitted.

``This is a voluntary program,'' Mr. Iannucci said. ``All the clients are told exactly what is on the unit.''

Legal experts like Mr. Clune dismissed that assertion, saying that psychiatric wards are sending the patients directly to the units and the patients have little say in the matter.