Major stock indexes fell by more than 1 percent Monday, dragged down by shares of Facebook and technology giants.

Facebook shares, which have been a key driver of the recent boom in technology, closed down by nearly 7 percent. The social media giant came under heavy fire from lawmakers in the United States and Britain over the weekend after news reports raised questions about whether it allowed third-party developers to access the data of users without their permission — a potential violation of its privacy agreement with the U.S. government.

Overall, the tech-heavy Nasdaq composite index dropped as much as 2.5 percent but rallied later to close down 1.8 percent.

Google parent Alphabet was down 3 percent, while Apple, Netflix and retail giant, founded by Washington Post owner Jeffrey P. Bezos, all finished down in the neighborhood of 1.5 percent. Shares of Silicon Valley darling Tesla closed down 2.4 percent.

The Dow Jones industrial average closed down roughly 335 points at 24,610.91 after dropping as much as 493 points. That finish is a 1.35 percent decline, with shares of blue-chip companies such as DowDuPont, 3M, IBM and Caterpillar all falling The Dow is down about 2,000 points from its high on Jan. 26 and is in negative territory for 2018.

The Standard & Poor’s 500-stock index, a broader measure of stocks, dropped 1.4 percent. All sectors were in the red, but the biggest losers were information technology, health care and energy.

Ali Mogharabi, an equity analyst with Morningstar, said investors are reacting to fears of greater regulatory scrutiny by both U.S. and European regulators of how Facebook uses its data.

“One of the most valuable intangible assets that Facebook has is its user data,” said Mogharabi. “They use that to make online ads more targeted and more effective. Additional regulatory steps in the U.S. could put user growth and/or revenue growth at risk.”

Volatility has continued to rattle markets, with fears that recently announced tariffs by President Trump could incite trade wars and put the brakes on global economic growth.

Investors are also eagerly awaiting the outcome of a two-day meeting at the Federal Reserve, the first under Chairman Jerome H. Powell. Most Wall Street observers expect the Fed to raise rates this week and at least twice more this year.

Adding to the uncertainty were several recent high-level departures at the White House and tweets by President Trump over the weekend, in which he railed against the Justice Department special counsel’s Russia investigation.

In recent weeks, Secretary of State Rex Tillerson was fired, while economic adviser Gary Cohn resigned. Both were seen as a moderating influences on Trump’s protectionist inclinations. White House communications director Hope Hicks, who was one of Trump’s longest-serving and closest aides, also resigned.

“The market is reacting to added uncertainty,” said Michael Farr, an investment manager in the District. “The president’s tweets over the weekend, combined with the turnover in senior staff, have investors questioning what’s next. Wall Street hates uncertainty, and we’re getting more of it.”

The so-called FAANG stocks — Facebook, Amazon, Apple, Netflix and Google-parent Alphabet — were among the ones hit hardest Monday.

“There’s a tug of war in the technology arena between unregulated social media companies and governments that want to regulate them,” said Ed Yardeni, president of Yardeni Research. “And the news of Apple developing its own next-generation screens is clobbering the shares of some of its suppliers. It’s a bad day for tech, for sure.”

Facebook, which has more than 2 billion monthly active users, announced Monday it had retained a firm to conduct a forensic audit of Cambridge Analytica. Lawmakers have asked the tech giant how Cambridge Analytica, a voter-profiling firm that has worked with Trump’s campaign and other Republicans, improperly collected personal information on Facebook users.

The number of Facebook users affected by the data grabbing could be more than 50 million.

Special counsel Robert S. Mueller III has reportedly requested documents from Cambridge Analytica for his investigation. The revelation underscores the power of social media networks and the unexpected ways in which technology companies can use data that users voluntarily give up. It also gives further hints to the important role big data plays in modern politics.

Trump targeted the special counsel on Twitter over the last several days, calling the investigation into the president “a total WITCH HUNT” and suggesting in a separate email that Mueller’s 17-member team is dominated by “hardened Democrats.”

Mueller is a former FBI director and a Republican.

The president’s Twitter missives earned criticism from Republicans on Capitol Hill, with Sen. Lindsey Graham (S.C.) cautioning the president against firing Mueller. Graham said such an action “would be the beginning of the end of his presidency.”