Yahoo has notified Facebook that the social networking giant may be infringing on 16 more of its patents.
Yahoo sent a letter to Facebook last month alleging that the patents "may be relevant" to technology Facebook uses in its servers and data centers, Facebook disclosed in a regulatory filing
Thursday. Facebook has data centers in Oregon and North Carolina.
Facebook said Yahoo had not threatened a lawsuit but had said "it may do so in the future." The company added that Yahoo's latest move was aiming at open-source and energy-efficient green technologies developed and employed by companies and engineers.
Facebook in March, alleging that the company was infringing on 10 of its patents. Facebook countersued
, asserting that Yahoo was infringing on 10 of its patents.