Leaders of the Senate Judiciary Committee said Wednesday they were seeking answers from the Obama administration about federal law enforcement’s use of surveillance technology that sweeps up basic cellphone data.

In a bipartisan letter to the departments of Justice and Homeland Security, Sens. Patrick Leahy, D-Vt., and Chuck Grassley, R-Iowa, described a recent policy change by the FBI that they said had left them with additional questions about how the equipment was used and about what privacy protections were in place.

“The Judiciary Committee needs a broader understanding of the full range of law enforcement agencies that use this technology, the policies in place to protect the privacy interests of those whose information might be collected using these devices, and the legal process that DOJ and DHS entities seek prior to using them,” the senators wrote.

Among the tools singled out in the letter is Stingray, a device that pretends it is a cellphone tower and tricks cellphones into identifying some of their owners’ account information. Law enforcement authorities have said the technology, which allows police to obtain cellphone information without having to ask for help from service providers, is useful for catching criminals, though civil liberties advocates have raised privacy concerns.

The senators say FBI officials have told their staff that the FBI recently changed its policy so that it now generally seeks a search warrant before using the cell-site technology, but with certain broad exceptions ? such as cases that involve a fugitive, pose an imminent public safety danger or in which the technology is used in a public place where no expectation of privacy would exist.

The senators demanded answers about how the FBI and other law enforcement agencies protect the privacy of people whose cellphone information is collected, even when they’re not targeted or suspected of any wrongdoing. The letter had a list of questions, including ones about how often the technology has been used and about how often law enforcement has requested a search warrant.

The Justice Department was reviewing the letter, said spokeswoman Emily Pierce. The FBI confirmed that officials had met with committee staff members and would respond to oversight questions, but otherwise referred questions about the letter to the Justice Department.

(AP)