Significant delays are anticipated at Terminal 2 tonight as a result of a power failure that caused a security breach shortly after 4pm at Sydney airport today. Delays were affecting Virgin Blue, QantasLink and Tiger Airways flights.

A statement on Sydney Airport’s website explains a walk-through security screening device had lost power, resulting in 16 passengers passing through without being properly screened.

"Accordingly, the decision has been taken to clear the area and re-screen all passengers," it said.

"Sydney Airport apologises to passengers for the inconvenience that this will cause and will be investigating the cause of the power loss to prevent a re-occurrence.

“Aviation security remains an absolute priority for Sydney Airport."

Passengers have now queued outside security screening gates which have yet to reopen. Delays of more than an hour to flights out of Sydney are anticipated.