Update: Death toll from Iran's southern port blast reaches 40, over 1,000 wounded

Iran has declared a state of emergency in the city of Bandar Abbas after a huge blast at the country's biggest port killed at least 28 people and injured more than 800, state media reported on Sunday.

The explosion on Saturday sent a huge plume of thick, gray smoke from the Shahid Rajaee section of the port complex, with media saying the blast was likely linked to chemicals being stored. Helicopters and aircraft dumped water from the air on the raging fire through the night into Sunday morning.

China's Consulate General in Bandar Abbas said three Chinese citizens sustained minor injuries in the explosion. They are now in good condition after receiving medical treatment.

The blast was so powerful that it was felt and heard about 50 kilometers away, according to semiofficial Fars news agency. An aerial shot showed fires burning at multiple locations, with authorities later warning about air pollution from chemicals such as ammonia, sulfur dioxide and nitrogen dioxide in the air. Schools and offices in Bandar Abbas were closed on Sunday.

Iran's President Masoud Pezeshkian has ordered an investigation and sent Interior Minister Eskandar Momeni to the site. The president urged "a comprehensive assessment of the causes of the incident "as soon as possible to prevent "the recurrence of such incidents in the future".

Speaking on Sunday at the scene, Momeni said the situation has stabilized in the main areas of the port, adding that six people remain missing as firefighters continue to work to fully extinguish the blaze.

The incident prompted authorities to declare a state of emergency in the city to safeguard citizens amid a "significant rise in air pollution".The governor of Hormozgan has declared three days of public mourning in the province.

Countries including Saudi Arabia, the United Arab Emirates, Iraq and Pakistan have extended condolences to Iran over the losses caused by the explosion.

Located near the strategic Strait of Hormuz, Shahid Rajaee is Iran's biggest container hub, covering 2,400 hectares and handling 70 million metric tons of cargo annually, including oil and general shipping. It has nearly 500,000 square meters of warehouses and 35 shipping berths.

No cause has been given for the explosion. Government spokeswoman Fatemeh Mohajerani said it would take some time to establish the cause, "but so far what has been determined is that containers were stored in a corner of the port that likely contained chemicals which exploded".

Nuclear negotiations

Also on Saturday, Iran held a third round of hourslong nuclear talks with the United States in Oman, with a promise for more talks and perhaps another high-level meeting next weekend. The two delegations were headed by Iranian Foreign Minister Seyed Abbas Araghchi and US Special Envoy to the Middle East Steve Witkoff.

Araghchi said the parties exchanged written points throughout the day in "very serious and work-focused" discussions.

"The atmosphere is good and both sides have seriousness. …However, whether an agreement can be reached or not, I am certainly hopeful but very cautiously."

A senior anonymous US official told The Times of Israel that the talks were "positive and productive". "This latest round of direct and indirect discussions lasted over four hours," the official said. "There is still much to do, but further progress was made on getting to a deal."

Oman's Foreign Minister Badr al-Busaidi, who has mediated the previous two rounds of talks, offered a positive note at the end of Saturday's negotiations.

Xinhua and agencies contributed to this story.