China has accused 11 government and port officials of negligence over the massive explosions that killed 139 people in Tianjin earlier this month.

It remains unclear whether they have been taken into custody.

However 12 company executives have now been formally detained, mostly from Ruihai International Logistics, which owned the warehouse that blew up.

The 12 August chemical explosions sent a huge fireball in to the sky and destroyed hundreds of homes.

At least 34 people are still missing since the blast, more than 500 are still in hospital and thousands have been unable to return home.

The explosions sparked concerns about the storage of dangerous chemicals and planning regulations.

At least three residential complexes were found to have been built within a 1km-radius of the warehouse, which flouted Chinese law.

'Illegal activity'

The 11 officials include the head of Tianjin's transportation commission Wu Dai, and Zheng Qingyue, the boss of Tianjin's port operator, a statement released through the Xinhua state news agency said.

Prosecutors said the government officials were variously suspected of approving Ruihai's bid to build a hazardous chemical warehouse in the port despite knowing the location broke safety regulations, and of helping the company to pass safety checks even though it did not meet the required standards.

Port officials were also negligent in their supervision of Ruihai's operations, said the statement, failing to detect "illegal activity" and safety issues around its handling of hazardous materials.

Ruihai arrests

Prosecutors have also named all 12 company executives who had been formally detained.

Among them is Ruihai's chairman, Yu Xuewei, and vice-chairman Dong Shexuan, as well as managers from the safety, finance, and operations departments.

Zeng Fanqiang, an evaluator from Tianjin Binhai Haisheng which conducts safety checks, was also detained.

The statement said the 12 executives were suspected of "being heavily responsible for the incident and of illegally storing hazardous chemicals".

The BBC's Celia Hatton in Beijing says the owners of the logistics company are thought to have used personal connections to illegally obtain licenses that allowed them to store hazardous chemicals close to a residential area.

News of the accusations comes days after China's work safety regulator Yang Dongliang was sacked for "serious breaches of discipline and the law".