Authorities in Marblehead are investigating a recent series of bicycle thefts in which the culprit replaces the stolen bikes with older, less valuable ones. 

During the last week, Marblehead police said several residents have found their bicycles missing from their property and replaced with bikes of lesser value, WHDH reported. There was not an apparent pattern or area of town that seemed to be targeted.

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"It's sort of one of those crimes of opportunity," Police Chief Robert Picariello told the Salem News. He recommended that residents lock up their bikes and said area kids were most likely responsible.

Police have also said that if anyone is seen leaving a bicycle and taking another, it is not part of program for sharing bikes, WHDH added.

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"If they have a bike, I don’t know why they need to get another one," 13-year-old Rei Newman, whose bike was recently stolen and replaced with an older one, said to NECN. "That’s what the police said — they just upgraded. They just threw a bad bike on the street."