Kelly J. Langmesser, a spokesman for the F.B.I., confirmed that the office was “conducting multiple searches in the Bloomingburg area in relation to an ongoing investigation.” In a statement, Joel Cohen, a lawyer for Black Creek Holdings, Mr. Lamm’s company, said “we feel confident when the dust settles they will find no wrongdoing.”

While 93 of the three-bedroom, 2,800-square-foot townhouses are already under construction in a muddy field here, Mr. Lamm, 54, a modern Orthodox Jew who is a son of Norman Lamm, a former president and chancellor of Yeshiva University, insists the development has not yet been marketed and will, come spring, be open to anyone of any faith to buy at between $369,000 and $389,000.

Nevertheless, Hasidim in Brooklyn’s Satmar community have published ads in Yiddish newspapers heralding a new Hasidic community in Bloomingburg with the name Kiryas Yetev Lev, an echo of an incorporated village farther south, Kiryas Joel near Monroe, of 21,350 Hasidim. (Yetev is a Hebrew acronym for Joel Teitelbaum, the grand rabbi who established the Satmar movement in the United States after the ravages of World War II and for whom Kiryas Joel was named.) Given that Hasidic families often have six to eight children or more, the development could more than quadruple Bloomingburg’s population.

Satmar leaders say that Hasidim, who are having difficulty finding vacant affordable apartments in Williamsburg and other Brooklyn neighborhoods, have been craving a satellite community. Mr. Lamm’s complex seems to fit their needs.