A Franklin Square man was arrested and charged with DWI under Leandra’s Law after police said he stopped the minivan he was driving, got out and approached an officer who’d stopped his friend — to explain to the cop that his friend wasn’t driving drunk.

Nassau County police said both drivers were arrested and charged with drunken driving following the 1:14 a.m. incident along the South Service Road of the Long Island Expressway near Lakeville Road in Lake Success.

The identity of the man arrested during the initial stop was not immediately available, police said.

More coverageComplete coverage: Suspected DWI crashes, arrests on LI

But police said the second driver, Michael A. Brown, 31, of Catalpa Drive, was arrested when the Third Precinct officer smelled alcohol on his breath after Brown stopped his black 2012 Chrysler minivan and approached him during the initial traffic stop.

Police said there were four children — two girls, 10 and 4; two boys, 10 and 9 — in the minivan driven by Brown.

The children were all released to the custody of a woman identified by police as Brown’s girlfriend.

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Police said she was a front-seat passenger.

There were no reported injuries.

Police said the officer at the scene “determined Brown was under the influence of alcohol” and said a subsequent investigation revealed “a clear plastic bag containing a green brownish substance believed to be marijuana” was found in the pocket of pants worn by Brown.

Brown was arrested and charged with four counts of aggravated driving while intoxicated under Leandra’s Law, as well as two other DWI-related counts and unlawful possession of marijuana, police said. He is now scheduled for arraignment Monday in First District Court in Hempstead.

Leandra’s Law is named for 11-year-old Leandra Rosado and makes it a felony, even on first offense, for someone to drive drunk with a child 15 years or younger in the vehicle. Leandra was killed when the car she was riding in overturned on the Henry Hudson Parkway in October 2009. That car was carrying Leandra and six other girls attending a sleepover party; the driver, Carmen Huertas, later pleaded guilty to DWI.