An airport spokesperson said that the concourse and gates have been evacuated.
Australian Federal Police are conducting a security check of the area; passengers have been directed to the check-in zone.
According to reports, at least one flight has been delayed.
"It is understood there was a fault with security screening equipment shortly after 2:00pm, allowing a small number of customers to enter concourse without property security screening," Adelaide Airport authorities said.
Airport authorities said that passengers will have to be re-screened amid the security incident.