China has formally detained 12 people over explosions in the city of Tianjin this month that killed at least 145 people.
11 officials and port executives have been accused of dereliction of duty or abuse of power.
Anger over safety standards is growing in China, after three decades of swift economic growth marred by incidents from mining disasters to factory fires, and President Xi Jinping has vowed that authorities will learn the lessons paid for with blood.
News of the detentions came a day after the ruling Communist Party sacked the head of the work safety regulator, a former vice mayor of Tianjin, for suspected corruption, but without making an explicit link to the 12 August chemical blasts.
The chairman, vice-chairman and three deputy general managers of Tianjin Ruihai International Logistics Co Ltd, owner of the warehouse that blew up, were among those who were "criminally detained", the state-run Xinhua news agency said.
The agency said in an English-language report they had been arrested.
In China, criminal detention precedes arrest, which happens only once police level formal charges.
Tianjin Port Holdings, the listed entity of the port's main operator, said it understood from the Xinhua website that its chairman, Zheng Qingyue, was being investigated for dereliction of duty and its vice-chairman was temporarily taking over his duties.
The company was operating normally, it said in a stock exchange statement.
Separately, the state prosecutor said on its website an investigation of the blasts had found officials from a range of agencies to have been irresponsible, negligent and lax in the supervision of Tianjin Ruihai.
Among these agencies were Tianjin's transport, land resources, work safety and customs offices, besides state-owned port companies.
It named 10 officials suspected of dereliction of duty and one suspected of abuse of power.
The death toll from the blasts that flattened part of the port, the world's tenth busiest, has risen to 145 with 28 people still missing, the Tianjin government said on its Weibo social media account.
