SAO PAULO — While flooding that has devastated Brazil’s Rio Grande do Sul state has yet to subside, another scourge has spread across the region: disinformation on social media that has hampered desperate efforts to get aid to hundreds of thousands in need.

Among fake postings that have stirred outrage: That official agencies aren’t conducting rescues in Brazil’s southernmost state. That bureaucracy is holding up donations of food, water and clothing. One persistent rumor contends that authorities are concealing hundreds of corpses, said Jairo Jorge, mayor of the hard-hit city of Canoas.

Jorge and other officials say hidden actors behind the postings are exploiting the crisis to undermine trust in government.

Ary Vanazzi, mayor of Sao Leopoldo, said many people ignored official warnings and instead heeded social media posts saying government alerts “were just politicians trying to alarm people.”

“Because of that, many didn’t leave their homes in this emergency. Some might have died because of it,” Vanazzi told The Associated Press. “Sometimes we spend more time defending against lies than working to help our population.”

Floods over the past two weeks have killed at least 149 people, and more than 100 remain missing, state authorities said Wednesday. More than 600,000 people have been forced from their homes.

Brazil became a hotbed for disinformation ahead of the 2018 election won by Jair Bolsonaro. During his presidency, adversaries often found themselves fending off digital onslaughts. The Supreme Court has since launched one of the world’s most aggressive efforts to stamp out coordinated disinformation campaigns, led by one controversial justice in particular who is overseeing an investigation into the spread of false news. He has ordered social media platforms to remove dozens of accounts.

The army was spared online mudslinging during the presidency of Bolsonaro, a former captain who is a fierce opponent of his successor, Luiz Inácio Lula da Silva. But it has become a target for far-right hostility under Lula, with social media users attacking military leaders for taking orders from the leftist president, said Alexandre Aragão, executive editor of fact-checking agency Aos Fatos.

Several videos posted online insinuate soldiers aren’t participating in rescues. Others mock soldiers’ supposed lack of equipment, using footage of a truck stuck in floodwaters. The general who leads the army’s southern command told CNN Brasil that one rumor claimed he was responsible for nonexistent deaths inside a hospital.

The army says it and local agencies deployed 31,000 soldiers, police and others to rescue more than 69,000 people and 10,000 animals and deliver tons of aid by air and boats. Brazil’s federal government announced it will spend nearly 51 billion reais ($10 billion) on recovery, provide credit to farmers and small companies and suspend the state’s 11-billion-reais annual debt service.

“These reports are disturbing, because they do not reflect reality,” the command said in a statement to the AP. “Many active military were also victims of these floods. Many soldiers have lost their homes after the rains and remain on the front lines helping the population.”

Prodded by complaints from military brass, Brazil’s government is appealing to social media platforms to stop the spread of misinformation, Attorney General Jorge Messias said in an interview.

As of late Tuesday, all had expressed willingness to cooperate — except X, according to Messias’ office. The platform’s owner, Elon Musk, recently railed against a Supreme Court justice’s decisions to restrict users’ accounts, accusing him of muzzling free speech and drawing praise from Bolsonaro and his allies. X didn’t immediately respond to an email requesting comment.

Messias’ office also filed a lawsuit against a social media influencer who claimed that a single businessman — and staunch Bolsonaro supporter — dispatched more aircraft to aid rescue efforts than the entire Brazilian air force. The government is demanding the right to reply on the Instagram profile of the influencer, Pablo Marçal, an outspoken critic of Lula with nearly 10 million followers.

The swarm of disinformation at a time of crisis amounts to a “tragedy within a tragedy,” Messias said. “When we stop everything to respond to fake news, we’re diverting public resources and energy away from what really matters, which is serving the public.”

Nearly one-third of people surveyed by pollster Quaest reported they were exposed to false news about the floods, according to the poll conducted from May 2-6. Conducted in 120 cities nationwide, it had a margin of error of 2.2 percentage points.

Disinformation is creating a hostile environment for aid workers. Locals have accused state and municipal agents of acting too slowly and threatened to expose them online, and yelled at firefighters over reports they’d failed to rescue people and pets, according to according to the mayors of Sao Leopoldo and Canoas. Some people pretending to be volunteers entered a warehouse of the state’s civil defense agency last week, filming aid donations inside and posting video online as supposed evidence of its failure to distribute the aid, according to the agency.

Last week, another falsehood contended authorities were halting trucks with donations, said Aragão. It was fueled by broadcaster SBT’s story about a truck stopped for inspection that, despite being overloaded, was later released. Social media posts distorted that report and claimed aid stoppages are a widespread phenomenon. The case was demonstrative, Aragão added.

“When there is a tragedy with the dimensions of what happened in Rio Grande do Sul, of course there will be isolated cases of absurd things,” he said by phone from Sao Paulo. “Social media sells those real and isolated cases as though they represent official protocol.”

Janine Bargas has been working nonstop on the disaster as a professor at the Federal University of Health Sciences of Porto Alegre in the state capital. Initially, her duties included providing reliable information, such as telling people where they could find needed medication.

Misinformation became so intense that her job now includes monitoring and debunking it. That has included recommendations for a bogus preventive treatment for a waterborne bacterial disease.

“The same anti-vaccine doctors who were recommending chloroquine during COVID started promoting a prophylaxis for leptospirosis,” Bargas told the AP, adding that panic over the reports erupted in a shelter managed by university staff. “People started fighting, asking for the medication. And this medication’s dosage can be very toxic for the liver.”

Jorge, the mayor of Canoas, became a target of disinformation just hours after the floods began. A post, shared millions of times on messaging apps, showed a brawl it said took place at a shelter in Canoas because of a decree that all donations pass through City Hall. The brawl actually took place in Ceara state, on the opposite side of the vast country, and Jorge issued no such decree.

The falsehoods are “orchestrated, aimed at making people stop believing in public agents,” he said. “Whenever a natural disaster happens, there’s a wave of solidarity. But not this time; there’s also a wave of anger caused by disinformation.”

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