Dismantling of the St. Ignatius Retreat House in North Hills has begun after local officials issued the permit to knock down the 93-year-old mansion.

The permit was issued on Monday, North Hills Village Mayor Marvin Natiss said Thursday.

The process of taking apart the 87-room "Great Gatsby"-era house began soon after the permit was issued, community leaders and residents said. It was not clear how long it will take until the building is demolished.

Preservationists were outraged, saying Long Island is losing one of its historic and architectural gems. They said the 72,000-square-foot Tudor Elizabethan retreat house could have been converted to a profit-making purpose, such as a hotel or condominiums.

"It is one of the grandest and most intact homes to come down in over 30 years" on Long Island, said Paul Mateyunas of Daniel Gale Sotheby's International Realty, a historian of the Island's famed Gold Coast. "It forever changes the landscape on the North Shore."

Loaded trucks this week have carted windows, mantels, doors and other items off the property, Mateyunas said local residents told him.

The Manhasset Bay Group Inc., the development company that bought the property in July for $36.5 million from the Jesuit order of Catholic priests, declined to comment Thursday. The Jesuits said it wasn't financially feasible to continue to run the retreat house.

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Local officials have said the group plans to turn the 33-acre property into a development of upscale single-family homes.

Natiss said he was taking no position on the sale and demolition, which he cannot halt.

"There's nothing I can do," he said. "It's their property. They're legally able to do whatever they want to do in terms of demolition."

The house, where the future Pope Pius XII stayed in 1936 during a tour of the United States, was completed in 1920 by the Catholic philanthropists Nicholas and Genevieve Brady. It also is known as Inisfada -- Gaelic for "Long Island."

Genevieve Brady donated the house to the Jesuit province of New York, which operated it as a seminary and then, for a half-century, as a retreat house. It closed in June.

Last month, tables, bookcases, chairs and other items were auctioned off, earning $50,000 for Jesuit-run Fordham University. The university used the money to help offset the cost of removing and transferring to its Bronx campus the mansion's magnificent St. Genevieve Chapel, which the Bradys had received permission from the Vatican to place in their home.

Preservationists tried to save the mansion through court actions and appeals to the new owners to convert it to another use.

In September, workers removed asbestos from the house, a move preservationists feared meant the wrecking ball was not far off.