The U.S. Justice Department has already opened a broad investigation of whether major digital technology firms engage in anticompetitive practices, the strongest sign the Trump administration is stepping up its scrutiny of Big Tech.

Following is a snapshot of the regulatory scrutiny that the technology bigwigs are under.

Senate Hearing

September 2019 - The Senate Judiciary Committee's antitrust panel questions chief U.S. antitrust enforcers from the U.S. Justice Department and the Federal Trade Commission. The regulators are expected to testify on their agencies' collaboration probing tech companies.

Department of Justice

July 2019 - The Justice Department announces a broad investigation into major digital technology firms, raises concerns about "search, social media, and some retail services online", hinting at the big tech companies.

September 2019 - Alphabet Inc Google discloses in a regulatory filing that it had received a civil investigative demand from the Justice Department on Aug. 30.

Federal Trade Commission

March 2018 - The U.S. Federal Trade Commission (FTC) confirms that it has opened investigations into Facebook Inc misuse of data with political analytics firm Cambridge Analytics.

July 2019 - FTC slaps a record $5 billion (£4 billion) fine on Facebook for mishandling privacy of its users with now defunct British political analytics firm Cambridge Analytica.

August 2019 - FTC launches an investigation into Facebook's acquisitions, accusing it of buying potential rivals.

U.S. states

September 2019 - New York state attorney general Letitia James announced an antitrust probe into Facebook led by New York and seven other states and the District of Columbia

September 2019 - Texas attorney general Ken Paxton's office announced an investigation of large tech firms but did not name the companies. It is expected to focus on Google and would look at both privacy and antitrust practices. The probe is likely to include up to 40 other states.

Other probes

July 2019 - Facebook agrees to pay the U.S. Securities and Exchange Commission $100 million for misleading investors about the misuse of its users' data.

August 2019 - A U.S. House of Representatives panel demands records of Apple Inc, Amazon.com Inc, Facebook and Google, including internal emails and financial information, by Oct. 14.

(Reporting by Neha Malara in Bengaluru; Editing by Maju Samuel)