The Pentagon is investigating how alleged secret U.S. and NATO plans for building up Ukraine’s military ahead of a planned offensive against Russia leaked online.

Versions of documents dating back to March 1 on assessments of Ukraine’s military strength and what Ukraine is expected to need before the offensive have surfaced on Twitter and Telegram, a messaging app with wide reach in Russia. The documents do not include battle plans or a date for when the push against Russia is expected to begin, but they contain a wealth of other information that had not been made public, according to The New York Times.