ISLAMABAD, Pakistan, June 12 — Several men believed to be American citizens have been taken into custody here during the past few weeks on suspicion of being linked to Al Qaeda, senior Pakistani officials said today. The Pakistani officials said most of the men had been picked up along with other suspected Al Qaeda and Taliban members in joint American-Pakistani raids in the country's remote tribal areas near the border with Afghanistan. They said they believe that the men form a disjointed network of disaffected Westerners who converted to Islam and have been drawn to militant causes, fighting alongside Al...