A wave of antitrust probe headlines on Facebook Inc. and Google parent Alphabet Inc. just yanked about US$137 billion from FANG stocks’ market values.

Some US$41 billion evaporated from Facebook on Monday as a person familiar with the matter said the U.S. Federal Trade Commission will oversee antitrust scrutiny into whether the firm’s practices harm competition in the digital market under an agreement with the Justice Department. That added to early-morning losses as the group was hammered by a report the Justice Department was preparing an antitrust investigation into Google. Some US$52 billion was erased from Google’s market value as the stock fell 6.9 per cent, on pace for the lowest close since Jan. 3.

The move comes as politicians from both parties face increasing pressure to apply tougher regulation on tech and telecom giants like Alphabet and Facebook Inc. and even break up the companies -- which are among the largest in the U.S. For investors, tougher regulation most likely means a negative impact on profits, making it harder to justify the rich valuations of some of the world’s highest-flying stocks.

Two FANG megacaps that were not directly targeted -- Netflix Inc. and Amazon.com Inc. -- also sold off sharply. Amazon plunged 4.7 per cent as about US$41 billion was wiped out of the e-commerce giant. Netflix lost US$2.5 billion from its market value as the stock fell 1.6 per cent.