A convicted sex offender who was released from custody in September because of the scandal at the now-closed state drug lab in Jamaica Plain was arrested Sunday morning after admitting to transit police that he stole 13 watches from a department store, authorities said.

Officers spotted Luis Quiles, 41, of Boston, and another man on a subway platform at Chinatown Station at around 10:15 a.m., huddled together in what appeared to be an attempt to conceal items from passersby, MBTA Transit Police said in a statement.