Internal Revenue Service criminal investigators will not continue to use cellphone-tracking technology without first seeking a warrant, the IRS commissioner told Congress in a letter made public Tuesday.

Commissioner John Koskinen said his agency is drafting a policy to abide by the Justice Department’s guidance on using the technology, which simulates cellphone towers to trick nearby phones into revealing their locations. The guidance requires a warrant — which requires probable cause and a judge’s signature —except in emergencies or exceptional circumstances.

Koskinen disclosed the new policy in a letter sent Nov. 25 letter to Sen. Ron Wyden, D-Ore.

The IRS said it has used its one cell-site simulator to track 37 cellular devices as part of 11 federal investigations since 2011. The technology was also loaned out on four non-IRS investigations, including a Drug Enforcement Administration case and three state cases. Koskinen said the device is used only by trained law enforcement agents for criminal investigations and won’t be used again until the new policy is in place.

The agency started the process of buying a second cell-site simulator in July but hasn’t yet received it. The letter was sent in response to question Wyden asked during a Finance Committee hearing last month.

Wyden and Rep. Jason Chaffetz, R-Utah, have introduced a bill requiring a warrant for government tracking of Americans’ electronic data, which includes the cell tower simulators. Wyden said in a statement that the IRS efforts were “reasonable steps to protect due process.”

“The IRS has an important role to play in combating money laundering, drug trafficking, and international tax dodging, but tax enforcement and protection of personal privacy must not be mutually exclusive,” he said.

(AP)