The shifting coverage about a deadly explosion at a hospital in Gaza highlighted the difficulties of reporting on a fast-moving war in which few journalists remain on the ground while claims fly freely on social media.

The first reports of a strike at the Ahli Arab Hospital in Gaza City came early Tuesday afternoon Eastern time. A spokeswoman for the Gaza health ministry said an Israeli airstrike had caused the explosion, killing at least 200 people. In a televised interview, a health ministry spokesman later said the death toll exceeded 500 — which the ministry later changed to “hundreds.”

The news changed quickly over a couple of hours. Many Western news organizations, including The New York Times, reported the Gazan claims in prominent headlines and articles. They adjusted the coverage after the Israeli military issued a statement urging “caution” about the Gazan allegation. The news organizations then reported the Israeli military’s assertion that the blast was the result of a failed rocket launch by Palestinian Islamic Jihad, an armed group aligned with Hamas.

On Wednesday, American officials agreed with Israel, saying early intelligence indicated that the launch did not come from Israel and instead was caused by the armed Palestinian group. Most of the coverage about the blast on Wednesday focused on the U.S. analysis.

But many supporters of each side had already made up their minds in the ensuing hours. Much of the Arab world united in support of Palestinians, with thousands of protesters marching in cities across the Middle East on Tuesday night and Wednesday, blaming Israel for the deaths of civilians at the hospital.

Kathleen Carroll, a former executive editor of The Associated Press, said the situation in Gaza was tough for news organizations to handle because they could not always get firsthand or verified accounts. As Israel prepares for a ground assault in Gaza, most Western journalists have evacuated the area, and reporters that remain face shellings and shortages of water, food and electricity.

The Committee to Protect Journalists said on Wednesday that at least 19 journalists had been killed during the conflict, 15 of them Palestinian.

“It’s extremely difficult,” Ms. Carroll said. “In Gaza, there are so few news organizations able to be on the ground and getting the kind of eyewitness reporting that helps.”

Covering wars is always fraught, both because journalists on the ground are often in harm’s way and because the sides at war aggressively push information in their favor.

The war between Israel and Hamas has proved even more difficult than most conflicts, because it has generated vast amounts of misleading and false information online. There are so many untrue claims that some people question the true ones.

It takes time to independently verify the claims from all sides. In the separate conflict between Russia and Ukraine, President Volodymyr Zelensky of Ukraine initially blamed Russia for a deadly missile strike on Sept. 6 in eastern Ukraine. But a New York Times investigation, published 12 days later, found that an errant Ukrainian air defense missile was most likely the cause. The investigation relied on combing through satellite imagery, missile fragments, witness accounts and social media posts.

The coverage of this week’s hospital blast generally represented what had been said about the explosion at the time of publication. The BBC’s initial breaking news report said, “Hundreds feared dead or injured in Israeli airstrike on hospital in Gaza, Palestinian officials say.” A later headline was “Israel denies airstrike on hospital in Gaza, saying failed militant rocket to blame.”

The Times sent a news alert at 2:51 p.m. Eastern time carrying the Palestinian assertion of an Israeli missile strike on the hospital. When the Israeli military statement came out, The Times sent another news alert on Israel’s assertion that “a misfired Palestinian rocket” was to blame.

Not all large global news outlets made similar changes. Al Jazeera, the news organization funded by the Qatari government, continued to report on Tuesday evening that Israel was to blame for the attack. It included a blog post with Israel’s denial, but added a comment from one of its own reporters, who said Israel regularly deflected blame for attacks that killed civilians on misfiring rockets. On Wednesday, Al Jazeera continued to report that the blast was an “Israeli attack.”

The BBC and Al Jazeera did not immediately respond to a request for comment. A Times spokesman said, “We report what we know as we learn it.”

“We apply rigor and care to what we publish, explicitly citing sources and noting when a piece of news is breaking and likely to be updated,” he said.

Bill Grueskin, a professor at Columbia University’s Graduate School of Journalism, said media organizations had to be “exceptionally careful” in dealing with news around the Israel-Hamas conflict, and should be transparent about where they are getting their information, “particularly when it’s from official channels that have vested interests in promulgating a particular point of view.”

Ms. Carroll echoed that sentiment, and said news organizations had to refrain from trying to fill in knowledge gaps with speculation.

“There’s so much mistrust on all sides and in all directions,” Ms. Carroll said. “It’s incredibly hard to walk that line, practically impossible to present a news story in whatever format that’s going to be believed by all parties.”