Nighttime thieves struck unlocked cars in Sag Harbor again last week, continuing a series of incidents that began in mid-December.Joan Baren reported the largest loss. She had parked her Subaru outside her Oakland Avenue residence on Christmas night, and returned to it on Dec. 27 to discover numerous items missing. Gone were $200 in cash, ferry tickets, “assorted maps and books,” and three watches, police reported. A few of the less valuable items were later recovered.Murat Ozsu, whose Jeep and Chevrolet were parked on Jermain Avenue from Christmas Day until Dec. 26, also called police on the 27th. This time the glove compartments were targeted; insurance cards, registrations, and an owner’s manual were taken.Ilona Polak lost a Dell laptop valued at $900 at about the same time from her 2014 BMW, which was parked near Main Street.Also reported on Dec. 27 was the theft of $800 in cash from a Ford parked on Main Street. The theft was reported by that vehicle’s owner, Maria Eftimiades.Sag Harbor Police Chief Austin J. McGuire said Tuesday that the department was actively investigating. “If you do see anything suspicious or have any information regarding these thefts, do not hesitate to call police,” he said. The number at the Division Street headquarters is 631-725-0247. “Please lock your cars when you park,” the chief said.