There were two levels of security at the stadium, run by both the Secret Service and Transportation Security Administration (TSA).
The latter is usually responsible for security at airports in the United States, with fans and media having to go through airport security-style scanners.
One member of the media said they, having reached an entrance, were told to go to a different queue as there were no security dogs available to search bags at that gate.
BBC Sport has been told by World Cup volunteers at the ground that the number of people arriving early before the game was much higher than the previous seven matches at the stadium.
Gates opened for supporters at 11:00 local time – four hours before kick-off – with more gates being opened sporadically to ease congestion.
It is not thought there will be any delay to kick-off or any other disruption to the match.