An off-duty Miami-Dade police officer was arrested after he was discovered passed out and drunk in his patrol car in the middle of a West Kendall intersection, the department said Thursday.

But Fernando Villa was not cuffed and booked into jail. Instead, Villa, 32, was allowed to go home after signing a form promising he would appear in court.

Now, the internal affairs bureau is investigating Villa, as well as why supervisors on the scene allowed him to avoid jail, despite orders from Miami-Dade Police Director Jim Loftus to treat him “like everyone else.”

“Someone along the line decided to depart from my specific directions,’’ Loftus said Thursday. “We’re going to discover the identity of the person or persons and hold them accountable.”

Villa, a Kendall district patrol officer, has been relieved of duty with pay as investigators probe the incident.

The episode happened in the Hammocks district in West Kendall. Another Miami-Dade officer found Villa’s idling patrol car around 8:20 p.m. Tuesday at Southwest 137th Avenue and 137th Street. Behind the wheel was Villa, dressed in shorts and a T-shirt, the department said.

Superiors were summoned and Loftus was telephoned. When explained the situation, Loftus said he ordered Villa be booked and arrested.

Under department policy, “promise to appear” notices are given in lieu of a physical arrest only for low-level misdemeanors, not felonies or DUIs. As is usual with promise-to-appear cases, a court date will not be set for several weeks.

It was unclear Thursday who drove Villa home or who made the decision to allow him leave.

Villa was previously a member of the department’s Special Response Team, which handles hostage and other dangerous situations. He was transferred back to road patrol after his unit was involved in the shooting deaths of four armed home invasion robbers in Redland in July.