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TEHRAN — Iran’s judiciary said Tuesday that it had arrested an undisclosed number of suspects involved in the accidental downing of a Ukrainian passenger plane that killed all 176 aboard last week.

The announcement came after days of protests shook Iran, with demonstrators railing against the government’s initial attempts to deny involvement in the downing of the plane. Thirty people were arrested during the demonstrations, a judicial spokesperson, Gholamhossein Esmaili, said at a news conference Tuesday.

Esmaili gave no further details on the number of those arrested in connection with the downing of the passenger jet and did not reveal their names or professions.

He also said that the plane’s black box had been taken to France for the data to be read and that more information would be released. But France’s bureau of aviation investigation confirmed to NBC News on Tuesday that no black boxes had been sent to France and nor were they expected to be.

Canada's transportation safety board had said Monday that the black boxes were damaged and remained in Iran.

"We haven't seen the extent of the damage, but extracting the data will pose some technical challenges for the Iranian investigating team," the head of the board said.

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Iran initially denied allegations that a missile had struck the plane shortly after it took off last Wednesday from Tehran, the capital, only to reverse course on Saturday and admit that it had shot down the jet by mistake.

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Iranian President Hassan Rouhani on Twitter Saturday blamed “human error” for the “horrific crash.”

Over the weekend, the U-turn prompted Iranian protesters to take to the streets demanding that Supreme Leader Ayatollah Ali Khamenei step down. Rouhani said that one person could not be held responsible for the downing of the plane and called for a special court to investigate.

Aniseh Bassiri Tabrizi, a research fellow at the Royal United Services Institute, a London think tank, said the way in which the government and the establishment handle the broader repercussions of the incident could be a "watershed moment for Iran."

"The choices it makes are likely to reverberate throughout Iranian politics and society for months, or even years, to come," she wrote in an analysis piece for the BBC.

Britain, France and Germany said Tuesday that they were triggering a dispute mechanism that is part of the nuclear deal with Iran, citing its failure to live up to terms of the pact.

The foreign ministers of the three nations said in a statement that they were "left with no choice, given Iran's actions, but to register today our concerns that Iran is not meeting its commitments."

But, they added, their countries would not join a campaign to implement maximum pressure against Iran and hoped that parties to the nuclear accord would find a way forward to resolve the impasse and preserve the agreement.

The 2015 nuclear deal between Iran and world powers eased international sanctions on Tehran in return for limits on its nuclear program. President Donald Trump withdrew the United States from the agreement in May 2018 and imposed economic sanctions on the country's oil industry, as well as banking and other key sectors.

Amin Hossein Khodadadi reported from Tehran, and Saphora Smith from London. Nancy Ing contributed from Paris, Oksana Parafeniuk from Kiev, and Tom Costello from Washington.

Reuters also contributed to this report.