Cops Grilling Bar About Jose Fernandez's Final Hours

The time Jose Fernandez and his friends spent in a popular Miami bar -- shortly before their boat wreck -- is now a focal point of the investigation into the Marlins star's death.

Law enforcement sources tell TMZ Sports ... cops have contacted American Social Bar & Kitchen to interview employees who were working late Saturday night/early Sunday morning. We're told they also want to check out surveillance videos to see if Fernandez and co. were drinking.

We broke the story -- the group was hanging out at the bar within 90 minutes of the accident.

Officials have said there was no physical evidence of booze at the accident scene. Investigators are awaiting toxicology results on the victims. Our sources say cops also got a search warrant for GPS and electronic data from the boat -- which was registered to Jose -- to nail down direction and speed when they crashed.

We're told one operating theory is the driver was attempting to go around the jetty, but misjudged it in the darkness ... at high speed.