New Jersey officials announced on Saturday six arrests in connection with the gang rape of a 7-year-old girl who investigators believe was sold for sex by her 15-year-old stepsister at a party in a Trenton high-rise last weekend.

The developments followed an intense, weeklong inquiry into what occurred on March 28 in a 13th-floor apartment at the Rowan Towers complex on West State Street, near the State Capitol. Officials said they expected to make more arrests in the coming days.

Investigators arrested one man, Gregory Joseph Leary, 20, of Trenton, on Thursday and charged him with raping the 15-year-old girl, whom the authorities did not identify. Another man Tiemear Lewis, 19, of Trenton, was also charged in the case, officials said.

Joseph L. Bocchini Jr., the Mercer County prosecutor, said his office would likely seek to try at least one of three juveniles who were charged, ages 17, 14 and 13, in adult court.