A second red flag was deployed at pre-season testing on Friday for another bizarre incident on the track.
Shortly after the afternoon session got underway, the red flag was thrown, forcing the drivers to come back to the pit lane.
It was not immediately clear why the red flag was deployed, however a replay then showed a bus driving across the run-off area.
In an obvious threat to driver and public safety, race control threw out the red flag so the bus could exit the circuit.
It was the latest strange reason for a red flag at testing this year after a glass panel that made up the start box gantry shattered during the morning session.
On Wednesday, running was halted for over an hour when a power outage plunged the circuit into darkness.
