WASHINGTON (AP) – The Transportation Security Administration violated privacy protections by secretly collecting personal information on at least 250,000 airline passengers, congressional investigators said Friday.

The Government Accountability Office sent a letter to Congress saying the collection violated the Privacy Act, which prohibits the government from collecting information on people without their knowledge.

The information was collected as the agency tested a program, now called Secure Flight, to conduct computerized checks of airline passengers against terrorist watch lists.

The GAO reported that about 100 million records were collected.