Federal agencies have used credit card transactions to track Americans without their knowledge.

A new document that was just released revealed that federal law enforcement agencies can get a so-called "Hotwatch" order. It allows agents to track someone under criminal investigation without a court order.

Agents then have access to credit card transactions, rental car agencies, calling cards and grocery store loyalty programs.

The order can be obtained by with a subpoena. The agent can then get an order from a judge saying the surveillance doesn't need to be disclosed.

The revelation highlights the U.S. Justice Department's growing power and willingness to track Americans with little to no judicial or congressional oversight.