Officials from the Chinese city of Tianjin, where two huge blasts killed at least 50 people, have revealed they discussed tightening safety standards with companies at the port just one week ago.

The explosions tore through an industrial area containing toxic chemicals and gas, ripping apart buildings, blowing out windows kilometres away, and injuring at least 700 people, officials and state media said.

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The People’s Daily newspaper said four fires were still burning 24 hours later.

The Tianjin Administration of Work Safety posted a notice about a meeting with companies handling dangerous chemicals at the port on its website on August 6.

It did not give a specific date of when the meeting took place.

The Xinhua news agency said the explosions, the first equivalent to three tonnes of TNT and the second to 21 tonnes of TNT, ripped through a warehouse owned by Tianjin Dongjiang Port Ruihai International Logistics.

The company’s website said it was a government-approved firm specialising in handling “dangerous goods”.

Company officials could not immediately be reached for comment.

China’s safety bureau said the company had violated packaging standards during a safety inspection two years ago.

Of 4,325 containers owned by Ruihai Logistics that were checked, five failed the inspection because packaging was sub-standard, the Tianjin Maritime Safety Administration said.

In a report, it said it had inspected more than 14,000 containers in total and found that 29 from the five firms had failed the packaging checks, with the main problem being inappropriate danger labelling.

The inspection report did not provide further details about what was wrong with the packaging.