On Monday evening, Sport Club Bahia – one of the biggest football teams in Brazil’s north-east – faced its rivals Ceará with black oil stains on their red, white and blue shirts. It was the latest sign of the growing outrage over a mystery oil spill that since early September has blighted a 2,200km stretch of some of the country’s most beautiful beaches – and the failure of President Jair Bolsonaro’s far-right government to handle the crisis.

Nobody knows where the oil is from or why it keeps washing up on Brazilian beaches. Yet while social media has been bombarded by videos of volunteers rolling up thick globs of oil in sand and putting them into plastic sacks, Bolsonaro sought to blame first Venezuela, then a “criminal action” to scupper a major oil tender. He has repeatedly attacked environmental protection agencies as a “fines industry” and has yet to visit affected areas.

“There is clear revulsion over the government’s inaction,” said Marcus Melo, a professor of political science at the Federal University of Pernambuco in the north-east. “The government has a certain myopia in understanding how serious this is.”

On Monday, Bolsonaro’s vice-president Hamilton Mourão announced that 5,000 more troops will be dispatched to help clean up the spill, but for many Brazilians the response was too little, too late.

Joel de Oliveira Filho, 57, proprietor of a guesthouse on Carneiras beach – one of the most famous beaches in the north-east state of Pernambuco – joined other local residents who started cleaning up oil with help from city hall employees. Nobody from federal government was there, he said.

“People in the north-east are cleaning the oil from the coast with their own hands while the federal government is immobile,” he said.

In nearby Bahia, volunteers organised the group Coast Guardians to clean beaches. It has 19,000 followers on its Instagram and has raised $4,800 online for protective gloves, boots and masks.

“This is civil society getting organised. Our movement does not support any political party, we support nature,” said Miguel Sehbe Neto, 37, a company administrator from Salvador who runs one of its 20 beach teams. “What we want is an explanation and effective action.”

Their team had help from naval personnel and environment agency staff when cleaning up two local beaches. But the government has not been able to map the slicks or stop them reaching the coast, he said – and many other beaches still need help.

People work to remove an oil spill on Suape beach in Cabo de Santo Agostinho, Pernambuco. Photograph: Stringer/Reuters

“We don’t know the size of the enemy,” he said.

Bolsonaro hosted a short Facebook live on Friday flanked by his defence minister, Gen Fernando Azevedo e Silva, and naval officers who explained they believe the oil came from a ship far out to sea.

Bolsonaro said containment barriers would not have stopped the oil as it was below the surface and suggested the spill could be a “criminal act” to prejudice a multibillion-dollar, “blockbuster” auction of oil prospecting rights on 6 November.

“Could it be a criminal act to prejudice this tender? It is a question that is in the air,” Bolsonaro said.

The environment minister, Ricardo Salles, has used Twitter to defend work by federal government environment agencies, state governments, the navy and state-run oil company Petrobras in dealing with the crisis.

However, Fabiano Contarato, an opposition senator who chairs the Brazilian senate’s environment committee, said the government “could have declared an environmental emergency […] They are not taking it seriously.”

Last Thursday he hosted a senate hearing with naval officers, environment ministry officials, prosecutors and the president of the environment agency, Ibama.

“They don’t know if it was a deliberate crime, they don’t know how to remove this oil,” Contarato said. “There are many more questions than answers.”

On Thursday federal prosecutors in the north-east ordered the government to put a national contingency plan into effect and said it had been “inefficient and ineffective”. But a judge ruled the plan was already operating and said the government was doing enough.

José Álvaro Moisés, a senior professor of political science at the University of São Paulo, noted that in April Bolsonaro’s government closed two committees that were part of Brazil’s national contingency plan for oil spills.

“The government’s position is against defending the environment,” he said.