United Nations investigators hoped they would get some help from Facebook when they asked to see information on suspected pirates operating in Somalia.

But Facebook responded with silence.

A report by the U.N. Monitoring Group on Somalia and Eritrea this month pointed out that while many private companies helped in the group's investigative work on matters such as piracy, al-Qaida-linked militants and government corruption, Facebook provided no such assistance.

Matt Bryden, a former coordinator of the Somalia monitoring group, said Tuesday that the U.N. group doesn't have subpoena power. He said he would expect Facebook to be cautious about sharing information because of pressure it has received over privacy issues.

Facebook did not respond to emails seeking comment.