The Department of Corrections is investigating how a photo of Rikers Island inmates flashing gang signs was posted on Facebook when inmates are banned from having cellphones.

The photo, posted to Facebook last Wednesday, shows a group of inmates in the back of a DOC van during a transport to Staten Island, the New York Daily News reported. It was posted to an account of a Facebook user believed to be an acquaintance of convict Rameen Smith, who was in the van at the time but is not pictured.

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At issue was the apparent use of a cellphone, which are off-limits to inmates though at least 10 were found in city jails last year, the Daily News stated.

"It is a major breach of security — it is contraband," a source said to the New York Post. "It could be used by prisoners to sell calls to other prisoners, which could lead to fights."

The DOC was investigating whether an officer passed the phone to Smith, the Post stated, adding that the foursome pictured in the photo were reputed members of a gang headed by Smith.

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"Commissioner [Joseph] Ponte has zero tolerance for the introduction of contraband into any DOC facility,” department spokeswoman Eve Kessler was quoted by the Daily News. "This matter is under investigation.”

The inmates’ cells were searched for the phone, according to the Post, but officials have been unable to recover it.