Fans were ejected from the grandstands by local police forces minutes before FP2 started at 2:30am local time in Las Vegas.
The session suffered a delayed start due to a drain cover issue that plagued FP1 and saw both Carlos Sainz and Esteban Ocon's cars significantly damaged.
Ferrari Team Principal Frederic Vasseur initially said it would be impossible for Sainz to make it back out for FP2, but the delay worked in their favour and they managed to get him out as did Alpine for Ocon.
But once track action did resume, fans were unable to watch it from the grandstands as workers had already left the track premises.
It is understood that the F1 Paddock Club also stopped its hospitality, while the Las Vegas Grand Prix promoter issued a statement on social media claiming fan areas were being closed.
It read: "Due to logistical considerations for our fans and our staff, we have made the determination that we will be closing all Las Vegas Grand Prix fan areas at 1:30am PT. We look forward to welcoming fans back later today for exciting FP3 and qualifying sessions."
As it was deemed unsafe for spectators to be in the stands without stewards, local authorities removed them from their seats - some of which cost upwards of $800 for the weekend.
FP2 got underway and the full 90 minutes went uninterrupted, with Charles Leclerc leading the timesheets from teammate Sainz.