Chinese courts Wednesday jailed almost 50 people over last year's giant explosions in the port of Tianjin that killed 165 people, state media reported.

The blasts at a chemical warehouse owned by Rui Hai International Logistics sent a huge fireball soaring into the sky and mangled structures kilometres away.

Social media users recorded the scene of what rapidly became the country's highest-profile industrial accident in years.

A swathe of the northern port was devastated and fears of toxic pollution were rife, with cyanide levels in the disaster zone far above national limits.

Those convicted on Wednesday were 24 company managers and staff members and 25 government officials, the official news agency Xinhua said.

The charges ranged from illegal storage of materials to abuse of power.

The head of Rui Hai, Yu Xuewei, received a two year suspended death sentence -- normally commuted to life in prison -- and was fined 700,000 yuan ($103,252) for his role in the disaster.

In the aftermath of the explosions Xinhua described Yu as a former executive at state-owned chemical company Sinochem, and said another of Rui Hai's owners was the son of the former port police chief.

Those connections helped the company get permits despite numerous safety violations, it reported.

The court ruling confirmed the findings of a government report in February, that government bodies in charge of the port, up to ministerial level, routinely ignored or violated laws and regulations on chemical storage.

Corruption is rife in China and causes widespread anger with the ruling Communist party.