The New York City Police Department is investigating why it took nearly nine hours for a police officer suspected of drunken driving to be given a blood-alcohol test on Friday.

Officer Rafael Casiano was off-duty when he crashed his car around 4:30 a.m. Friday on the Cross Bronx Expressway.

Breathalyzer tests taken later that afternoon showed his blood alcohol content was below the legal limit of 0.08.

After interviewing medical personnel and obtaining a warrant for Casiano's blood, investigators placed the officer under arrest and charged him with driving while intoxicated.

Casiano has been suspended from the NYPD.

His 36-year-old partner, Officer Keith Paul, sustained serious head injuries in the crash.