Superstorm Sandy appears to have rendered unusable some evidence collected by the NYPD in criminal cases, and officials are trying to assess whether the losses will affect ongoing prosecutions.

NYPD Commissioner Ray Kelly said the evidence "may very well" have been marred when floodwaters inundated some police precincts and offices in low-lying areas of Brooklyn and Queens.

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"This is an issue that will have to be looked at on a case-by-case basis," said Kelly, who couldn't estimate the size of the losses.

For the most part, evidence is kept only for a short time at precincts, said Kelly, indicating that any spoiled items such as DNA materials would have been connected to recent arrests.

Among the precincts impacted by the storm surge was the 60th in Coney Island, which was heavily damaged and had to be evacuated. Two floors of the station house were flooded and three walls of the basement collapsed, said officials. Headquarters for the housing police command were also flooded, as was the 100th Precinct in Rockaway.

Evidence losses have happened before in catastrophes. During 9/11, federal investigators lost evidence or saw some damaged in drug, securities and other cases. Some of the materials were reportedly stored in offices of law enforcement agencies housed in places such as Six and Seven World Trade Center.