A House investigation into tech competition may have testimony from some of the biggest names in the industry — if they agree, at least. Axios understands the Judiciary Committee has asked Apple, Alphabet, Amazon and Facebook to say if their CEOs will testify for the antitrust probe in July. The companies reportedly have until June 14th to answer. However, they might not have a choice regardless of their responses — the letters hint at possible subpoenas for testimony and relevant documents if the CEOs don’t volunteer.

In statement, committee chair David Cicilline said the documents (which include responses to other probes) were “essential” to the investigation and that requests like this were part of the “appropriate process” to obtain the files.