The red flag was shown just moments after track action had resumed after lunch on the final day of pre-season testing.
It was triggered by a bus traversing the run-off at Turn 10, the left-hander onto the back straight at the Bahrain International Circuit.
The movement had not been approved by race control which quickly moved to neutralise the circuit due to the obvious safety issues the vehicle raised.
The bus appeared to be moving from the rear of the paddock area towards Turn 4.
Though an access road exists around the perimeter of the circuit, behind barriers, the vehicle instead took a more direct route across the run-off area while cars were on track at full speed.
Speedcafe understands that while no specific investigation has been launched for that incident, the FIA reviews all incidents and provides feedback to relevant stakeholders and ensures any necessary action is taken.
Vehicles on track have come under intense scrutiny in recent years.
In 2015, Jules Bianchi died from injuries he sustained after colliding with a recovery vehicle at the 2014 Japanese Grand Prix.
Since then, there has been little tolerance for similar incidents, with Pierre Gasly apoplectic when he encountered a vehicle on track during the 2022 edition of the Japanese Grand Prix.
The Bahrain International Circuit hardly covered itself in glory during F1 testing.
Earlier in the day, a glass panel fell out of the start gantry and onto the front straight where it shattered, drawing red flags.
It was the second time running had been interrupted due to circuit faults, after a power failure halted proceedings on the opening afternoon.
A regional power failure saw the floodlights shut off while cars were on track.
Power was also lost in the pit lane, which led to the day’s running being extended by an hour to make up for the lost time.
It raised questions around how the lights are powered, and what backup facilities are in place should there be a power cut.
Fortunately, the Wednesday outage occurred before the sun had set but as the light was beginning to fade.
April’s Bahrain Grand Prix will begin at 18:00 local time as the sun sets.
