U.S. Attorney General William P. Barr blasted Big Tech on Wednesday, raising the specter that Silicon Valley might soon be held accountable for a wide array of dangerous, harmful content that critics say has flourished on their sites and services.

At an event that laid bare tech’s broad troubles — including the spread of terrorism, illicit drug sales and child sexual exploitation online — Barr said it may be time for the government to seek sweeping changes to a key portion of federal law, known as Section 230, that long has spared tech companies from liability for content posted by their users.

“No longer are tech companies the underdog upstarts,” Barr said in a speech, reflecting on the origin of the statute. “They have become titans.”

Barr’s comments came during a day-long summit focused on the law, which aimed to study whether the decades-old federal safeguards that helped incubate the Internet have become hindrances, preventing law enforcement and aggrieved users from obtaining justice when people are harmed.

But the volatility of the debate flared repeatedly during a second, private gathering later in the day with top officials, tech giants and other digital experts.

In raising a series of issues around Section 230, DOJ officials at one point asked if social media platforms should be held liable for decisions they make around political speech, according to two people with knowledge of the meeting who requested anonymity because it was supposed to be off-the-record. That sparked into a heated debate among participants over allegations that social-media companies are biased against conservatives, a charge repeated by President Trump — yet one that Facebook, Google and other companies deny.

A Justice Department aide, taking no position on the issue, initially described the fight over political speech as the “800-pound elephant in the room," the sources said. Those leveling the charges of censorship, according to the sources, included a participant from the Media Research Center’s TechWatch initiative, which asserts on its web page that “a handful of tech companies can censor both the people and the ideals of the right."

DOJ declined to comment. A spokesman for Media Research Center did not respond to requests for comment.

The Justice Department has been exploring Section 230 as part of a wide-ranging probe of Facebook, Google and other companies, an inquiry that’s also studied whether those firms have become too big, powerful and anti-competitive. Justice officials have signaled they plan to put forward recommendations — and potentially bring individual cases against companies — before the end of the year.

For regulators, their concern is that Facebook, Google and other tech giants -- despite connecting once disparate communities -- have served as conduits for harm and abuse. They’ve unwittingly housed hate speech and extremism, and helped spread graphic, viral videos of violent acts, including the deadly attack in Christchurch, New Zealand, last year. They’ve become marketplaces for the sale or promotion of guns, drugs and fake medical cures. And they’ve been weaponized to spread misinformation and undermine elections, including in the United States. Often, they’re able to dodge direct punishment even when their technologies are used to enhance the reach of such harmful material, critics say.

Lobbyists from Facebook, Google and other online platforms have fought vigorously in response to protect their prized legal shield, arguing it actually gives them cover to do the sort of content moderation that governments seek — without being sued for the decisions they make about the posts they leave up or take down.

“Certainly, more can be done,” Matt Schruers, president of the Computer & Communications Industry Association, said in a public panel discussion. The group represents Amazon, Facebook, Google and other tech companies. “I don’t think we should assume the misconduct of a few bad actors is generalizable across a large industry."

But Barr -- who cautioned earlier Wednesday he had not come to a final position on whether Section 230 should be significantly revised or repealed — still highlighted the law’s “expansive reach,” a comment that could encourage members of Congress who have floated similar suggestions about changes to the law.

Amid withering criticism, many in the industry have emphasized their recent work to improve their policies, hire more people to review content and take swifter, more aggressive action to ensure users aren’t harmed. Yet their assurances have failed to assuage regulators even beyond Washington: Throughout the European Union, for example, policymakers have contemplated a raft of fines and other punishments in the event Facebook, Google and their peers fail to prevent or disable dangerous posts, photos and videos in real time.

The regulatory threat has grown so dire that Facebook chief executive Mark Zuckerberg paid a rare visit to Brussels on Monday. Ahead of his visit with E.U. officials, the social-networking giant articulated its position on regulation, arguing in a white paper that laws that “punish the publication of illegal speech are unsuitable for the internet landscape.”

But the idea appeared to find an icy reception among the European Commission, where some members have pushed the company to play a more active, aggressive role in policing the Web for harm. “Facebook cannot push away all the responsibility,” Vera Jourova, the E.U. vice president for values and transparency, told reporters.

In Washington, top officials on Wednesday sought to make their own case about the need for Facebook, Google and their peers — with vast reach and once unfathomable profits — to be held more accountable for their role in facilitating the spread of dangerous posts, photos and videos.

“We’re constantly reminded that the same technology that facilitates free speech, connects with our loved ones and our friends and enriches our lives can pose serious dangers,” FBI Director Christopher A. Wray said to open an event on Section 230.

The full scope of DOJ’s interests surfaced at its private gathering with top officials, tech giants and other digital experts late Wednesday. DOJ officials raised a series of potential tweaks to the law, describing their attempts to solicit feedback as a “launch point” for future reform, according to four people familiar with the gathering.

DOJ officials did not endorse any specific reform to Section 230. But one of the ideas top aides proposed for discussion essentially would require Facebook, Google and other tech giants to take certain steps in order to earn protection under Section 230 from lawsuits and other punishments, three people familiar with the meeting said. The idea tracks with ideas expected soon in a draft bill led by GOP Sen. Lindsey Graham (S.C.), the sources said.

Speaking Wednesday in a public setting, Carrie Goldberg, an attorney who specializes in sexual privacy violations, offered one example of the potential harm from her own case work: A plaintiff whose ex repeatedly created fake profiles of him on Grindr, a gay dating app, putting him at risk for assault.

The ex would “post my client’s geographic information, and then send people” to his home and workplace, looking for sex, Goldberg said. The plaintiff repeatedly flagged the issue to Grindr, to no avail, and a subsequent lawsuit fell short of holding the company accountable in court. Grindr prevailed by invoking Section 230, she said.

“They see Section 230, and all the case law over the past few decades … as a pass,” Goldberg continued, “and take no action whatsoever.”