Media companies Associated Press, Gannett Co. and Vice Media LLC have sued the FBI asking it to disclose the vendor behind the unlocking of the iPhone in the San Bernardino case and the amount of the payment made, reports the Los Angeles Times.

The case was filed under the US Freedom of Information Act, citing no legal basis to withhold the information. Earlier requests to reveal the secret deal were turned down by the government agency.

“Understanding the amount that the FBI deemed appropriate to spend on the tool, as well as the identity and reputation of the vendor it did business with, is essential for the public to provide effective oversight of government functions and help guard against potential improprieties," said the suit.

The iPhone belonged to Syed Rizwan Farook who killed 14 in last year’s San Bernardino shootout. The investigators wanted the phone hacked for information on the killer and sought the services of an unidentified vendor after Apple refused to do it on client privacy grounds despite a court order.

For details, read the L.A. Times report.