Angry protesters at a building collapse in southwest Iran that killed at least 31 people shouted at the envoy of Supreme Leader Ayatollah Ali Khamenei, leading to a crackdown in which riot police beat protesters, according to online videos, and fired tear gas.

The protest openly questioned the Iranian government’s response to the disaster a week ago, when pressures mounted in the Islamic Republic over rising food prices and other economic problems amid the unraveling of its nuclear deal with world powers.

And while the protests seem leaderless so far, even Arab tribes in the region appeared to have joined them on Sunday, raising the risk of escalating unrest. Tensions have already escalated between Tehran and the West after Iran’s Revolutionary Guards seized two Greek oil tankers on Friday.

Ayatollah Mohsen Heydari al-Kasir tried to address the mourners near the 10-storey Metropole building in the city of Abadan, but the hundreds who gathered there booed and screamed.

Surrounded by his bodyguards, the ayatollah, in his 60s, tried to carry on but could not. “What is happening?” The cleric asked for a bodyguard, then leaned forward to say something to him.

The clergyman again tried to address the crowd: “Dear people, please remain calm as a sign of respect and love for Abdan and his martyrs.” [victims] The entire Iranian people mourn tonight.”

The crowd responded by shouting: “Shameless!”

Then the live broadcast of the event on state television was interrupted. The demonstrators later chanted, “I will kill, I will kill whoever killed my brother!”

The Tehran-based daily al-Hamshahri and the semi-official Fars news agency said protesters had attacked the platform where state television had installed its camera and disrupted broadcasts.

Police ordered the crowd not to chant anti-Islamic Republic slogans and ordered them to leave the gathering, calling the gathering illegal. A video later showed officers confronting and beating protesters with batons as clouds of tear gas erupted. At least one officer fired what appeared to be a rifle, though it was not clear whether it was live fire or “beanbag” rounds intended to stun.

It was not immediately clear if anyone was injured or if the police were arresting them.

Details in the videos analyzed on Monday matched well-known features in Abadan, 410 miles (660 km) southwest of the capital, Tehran. Foreign Farsi television channels reported tear gas and other gunfire.

Independent intelligence gathering remains very difficult in Iran. During the unrest, Iran cut internet and telephone connections to the affected areas while restricting the movement of journalists within the country. Iran is ranked by Reporters Without Borders as the third worst country in the world for journalists – after North Korea and Eritrea.

After the tower’s collapse in Abadan last Monday, authorities admitted that the building’s owner and corrupt government officials had allowed the building to be built despite concerns about poor workmanship. Authorities have arrested 13 people, including the city’s mayor, as part of an investigation into the disaster.

According to the official Iranian news agency, rescue teams retrieved two more bodies from under the rubble on Monday, bringing the death toll to 31. The authorities fear that more people may fall under the rubble.

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The fatal collapse raised questions about the safety of similar buildings in the country and highlighted the ongoing crisis in Iran’s construction projects. The collapse reminded many of the 2017 fire and collapse of the Plasco building in Tehran that killed 26 people.

In Tehran, the city’s emergency department has warned that 129 high-rise buildings in the capital remain unsafe based on a 2017 survey. The country’s public prosecutor, Mohammad Jafar Montazeri, has promised to address the issue immediately.

Abadan has seen previous disasters. In 1978, an arson attack at Cinema Rex – a few blocks from the collapsed building in modern Abadan – killed hundreds. Anger over the fire sparked unrest in the oil-rich regions of Iran and contributed to the outbreak of the Islamic revolution that toppled Shah Mohammad Reza Pahlavi.

Abadan, in Iran’s oil-rich Khuzestan province, is home to Iran’s Arab minority, who have long complained of being treated as second-class citizens. Arab separatists in the region have in the past carried out attacks on pipelines and security forces. Video clips and Al-Hamshahri newspaper indicated that two tribes entered the city to support the protests.