An Iraqi defector who described himself as a civil engineer said he personally worked on renovations of secret facilities for biological, chemical and nuclear weapons in underground wells, private villas and under the Saddam Hussein Hospital in Baghdad as recently as a year ago.

The defector, Adnan Ihsan Saeed al-Haideri, gave details of the projects he said he worked on for President Saddam Hussein's government in an extensive interview last week in Bangkok.

Government experts said yesterday that he had also been interviewed twice by American intelligence officials, who were trying to verify his claims. One of the officials said he thought Mr. Saeed had been taken to a secure location. The experts said his information seemed reliable and significant.

The interview with Mr. Saeed was arranged by the Iraqi National Congress, the main Iraqi opposition group, which seeks the overthrow of Mr. Hussein. If verified, Mr. Saeed's allegations would provide ammunition to officials within the Bush administration who have been arguing that Mr. Hussein should be driven from power partly because of his unwillingness to stop making weapons of mass destruction, despite his pledges to do so.

Mr. Saeed's account gives new clues about the types and possible locations of illegal laboratories, facilities and storage sites that American officials and international inspectors have long suspected Iraq of trying to hide. It also suggests that Baghdad continued renovating and repairing such illegal facilities after barring international inspectors from the country three years ago.

Spokesmen for the Central Intelligence Agency and the Defense Department's Defense Intelligence Agency declined to comment about Mr. Saeed or whether they had interviewed him.

Charles Duelfer, the former deputy chairman of the United Nations panel once responsible for weapons inspections in Iraq, said that Mr. Saeed's account was consistent with other reports that continue to emerge from Iraq about prohibited weapons activities. "The evidence shows that Iraq has not given up its desire for weapons of mass destruction," said Mr. Duelfer, who was the highest-ranking American on the United Nations panel.

Evading Restrictions

In the interview, Mr. Saeed said Iraq had used companies to purchase equipment with United Nations blessing, and then secretly used the equipment in its unconventional weapons program. One such firm, he said, was Leycochem, a construction materials company based in Cologne, Germany, that has long done business in Baghdad and other Middle Eastern countries.

In a telephone interview today, Jrgen Leyde, the managing director of Leycochem, said that his limited contracts with the Iraqi ministries of oil and industry have nothing to do with unconventional weapons and had been approved by the United Nations.

Separately, Mr. Saeed had told representatives of the Iraqi National Congress, which helped Mr. Saeed flee Iraq last August, that Iraq had tested chemicals and biological agents on Shiite and Kurdish prisoners in 1989 and 1992 at undisclosed sites in the Iraqi desert.

Mr. Saeed said that his work for the government's Military Industrialization Organization and for a company associated with it, Al Fao, continued until just before he was arrested on what he called trumped-up fraud charges and imprisoned last January in Hakamiya, where political prisoners are held. He said that he bribed his way out of jail last summer and fled Iraq after receiving a tip that he would soon be re- arrested.

To support his account, Mr. Saeed provided copies of contracts, including one involving his company, the Iraqi industrialization group and Al Fao.

Mr. Saeed said that several of the production and storage facilities were hidden in the rear of government companies and private villas in residential areas, or underground in what were built to look like water wells which are lined with lead-filled concrete and contain no water. He said that he was shown biological materials from a laboratory that was underneath Saddam Hussein Hospital, the largest hospital in Baghdad.

Mr. Saeed said that he had not personally visited the lab and was not certain whether it was a storage facility for germs and other materials to be used in the program or a place where actual research and development was conducted.

"They brought me this material to ask me whether or not it had expired," he said. The Iraqis and another contractor who brought him the material to examine "told me where, and the conditions under which it was stored, and asked me to tell them whether it might still be good, even though it had been kept beyond the expiration date."

Visits to 20 Sites

He said, however, that he had personally visited at least 20 different sites that he believed to have been associated with Iraq's chemical or biological weapons programs, based on the characteristics of the rooms or storage areas and what he had been told about them during his work. Among them were what he described as the "clean room" of a biological facility in 1998 in a residential area known as Al Qrayat.

Most of the time, he said, no research or development was going on at those places while he visited, because his work involved preparing the rooms to be used for such dangerous research. Mr. Saeed said that his company had specialized in filling cement cracks in the floors and walls of such facilities, lining their floors and walls with layers of epoxy paste and other substances that would prevent leaks and enable them to be easily decontaminated, and injecting cement walls and floors with additives to resist chemical corrosion.

Mr. Saeed said that over the years he had also picked up some odd jobs. In 1999, for instance, associates in the Iraqi intelligence service had asked him to help them design a better glue for the Defense Department's hand grenades. "I devised a better glue for them," he said, "which could hold together at higher levels of heat."

Not all of his work was for the military, he said. In 1998, he received part of the contract to build the sauna rooms, swimming pool, and gym of Al Salaam Palace, one of the many lavish, sprawling palaces that Mr. Hussein had built. He said he had also built Mr. Hussein's first whirlpool bath.