ISLAMABAD, Pakistan — An army officer and a businessman have been detained as part of a widening inquiry into a circle of Pakistanis who had some knowledge of the activities of the man charged with trying to set off a crude car bomb in Times Square, according to a Western official and an American intelligence official.

The army officer was arrested in Rawalpindi, the garrison city that serves as the headquarters of the Pakistani Army, the American intelligence official said. He appeared to have been disaffected, and his involvement with Faisal Shahzad, the Pakistani-American charged with the failed bombing in New York, did not signal the involvement of the Pakistani Army in the attack, the intelligence official said.

The arrest of the officer, who holds the rank of major and whose name was not disclosed, and of Salman Ashraf Khan, 35, an executive of a catering company that organized functions for the American Embassy here, suggested the participation of a group of Pakistanis in helping Mr. Shahzad after he returned to Pakistan from the United States last year to plan the bombing, the officials said.

Several other Pakistani men have been arrested in the Islamabad area in connection with the case, according to a Pakistani intelligence official who did not offer details about the men’s backgrounds.