WASHINGTON (AP) — Some warehouse workers who fill orders for Amazon.com customers say they spend up to 25 minutes after every shift waiting to pass through security checks to make sure they aren't stealing from the online retailer. But they don't get paid for the extra time.

The Supreme Court is hearing arguments Wednesday in a lawsuit filed by two former staffers at a Nevada warehouse who claim they should be compensated for time spent in security screenings under the Fair Labor Standards Act.

A ruling in favor of the plaintiffs could subject employers to billions of dollars in retroactive pay and increase costs for companies that have expanded security measures to curb employee theft. But it could also mean a slight boost in wages for millions of employees forced to spend extra time going through security.

Integrity Staffing Solutions Inc., the independent contractor that provides staff for Amazon.com warehouses, claims no extra pay is required because the security clearances are unrelated to the workers' core job duties.

The company requires departing workers to walk through a metal detector and remove wallets, keys and belts to make sure no merchandise has been stolen. The process takes time because hundreds of employees line up to leave at once, causing long lines.

A federal judge sided with the company, but the 9th U.S. Circuit Court of Appeals reversed the ruling. The appeals court said the security clearance was necessary to the primary work performed by warehouse workers and it was done for the employer's benefit.

Integrity Staffing argued in a brief to the court that a security screening "is no more integral or indispensable to warehouse work than time spent commuting, walking from the parking lot to the work place, waiting to pick up protective gear, or waiting in line to punch the clock."

The 9th Circuit ruling last year has spawned at least four class-action lawsuits against Amazon.com seeking compensation for time spent in post-shift security screenings. Similar suits are pending against CVS Pharmacy and Apple Inc., seeking to represent tens of thousands of workers.

The Obama administration has sided with the company, saying in a brief that security screenings are not "integral and indispensable" to the work performed by the warehouse employees. It says the screenings at the end of employee shifts "were not closely intertwined with their principal activity of filling orders in the warehouse."

The administration also cites a Labor Department opinion letter that makes no distinction between searches for general security and those to prevent theft, finding neither requires pay.

Business groups, including the U.S. Chamber of Commerce, say in court filings that security screenings are essential to prevent employee theft, which costs the retail industry an estimated $16 billion a year.

Requiring companies to pay workers for going through security, they argue, "would force employers to choose between incurring greater costs to retain security screenings" and "forgoing or reducing security measures so as not to incur additional labor costs."

The case is Integrity Staffing Solutions Inc. v. Busk, 13-433.