Image caption Airport security staff screen millions of items of luggage each year

Four current and former security screeners at Los Angeles international airport have been arrested and charged with drug-trafficking and bribery.

The four accepted cash to allow large shipments of cocaine, methamphetamine and marijuana through X-ray machines, the US justice department said.

The charges allege 22 separate payments of up to $2,400 (£1,500) allowed drug-runners to bypass airport security.

A prosecutor said they "placed greed above the nation's security needs".

"The allegations in this case describe a significant breakdown of the screening system," Andre Birotte said.

"Airport screeners act as a vital checkpoint for homeland security, and air travellers should believe in the fundamental integrity of security systems at our nation's airports."

Two of the four accused are current employees of the Transportation Security Administration (TSA), while the other two used to work for the organisation.

The current employees, John Whitfield, 23, and Capeline McKinney, 25, are accused of allowing shipments of more than 20kg (44lb) to pass through a screening area while they were on shift.

Former TSA screener Joy White, 27, is accused of a similar offence, while Naral Richardson, 30, is alleged to have made arrangements for shipments to pass unhindered.

Other individuals named in the indictment are accused of being part of the smuggling ring, several working as drug mules.

Special Agent Briane Grey of the Drug Enforcement Administration (DEA) said the accused "traded on their positions at one the world's most crucial airport security checkpoints".

The TSA, created in the wake of the 9/11 terror attacks, is part of the US Department of Homeland Security and has responsibility for screening millions air passengers and huge quantities of luggage and freight each year.

The agency faces frequent criticism from passengers who accuse screeners of over-zealous physical examinations. Over the past week an account posted on Facebook accusing agents of requiring a pat-down of a four-year-old girl has put the TSA back in the spotlight.

A former head of the TSA, Kip Hawley, recently wrote in the Wall Street Journal that the US security system was "broken" and needed root-and-branch reform.