The “Cyber Rodeo at Giga Texas”, an invitation-only party for thousands of guests at Tesla's new billion-dollar-plus “Gigafactory” in Austin, was the biggest secret and the toughest ticket in town on Thursday.

As many as 15,000 people were expected to attend the private event hosted by Tesla mogul Elon Musk to mark the opening of the new factory in Travis County that also serves as the company's new home following its move from California.

A county-issued permit said the event included interactive tours, food, alcohol and live entertainment. But the event was off-limits to the general public and the news media.

Musk has said the plant, which would employ up to 10,000 workers, would build its Cybertruck, Semi, Model 3 and Model Y sport utility vehicles. Last month, he also opened another “Gigafactory” on the outskirts of Berlin to produce the Model Y SUV.