NEW YORK (CBSNewYork) — The NYPD says the culprits who have been covering entire trains with graffiti may be traveling vandals.

Recently, several trains had to be taken out of service after they were covered top to bottom in paint.

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Authorities say the trains were targeted while they were in tunnels between stations.

An E train completely covered in graffiti on Jan. 29, 2020. (credit: CBS2)

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Police say these vandals may not be New Yorkers.

“We certainly have homegrown people that do graffiti from time to time, but we also have people that do this for a living and they come here and they travel from city to city, in some cases from out of the country,” Police Commissioner Dermot Shea said.

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The NYPD says it has teams that work with international police to track these vandals.

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It costs the MTA thousands of dollars to clean each train.