Tianjin International Ruihai Logistics, the Chinese company whose warehouse in Tianjin exploded last week killing at least 114 people, did not have a license to handle hazardous chemicals until two months ago, Xinhua news agency says.
The news agency also said that for eight months before June, the company handled hazardous chemicals without the right documents.
Nearly 700 people were injured in August 12 devastating blasts.
Ceremonies in the port city honored the dead on August 18.
Cargo ships blared their horns and people gathered in silence to mark the day.
Tianjin residents have been staging protests demanding compensation for property damage from the government.
Thousands of people had to evacuate their homes after toxic chemicals were detected in the air following the blasts at the world’s 10th-busiest port.
Some 17,000 homes were damaged by the explosions and their shockwaves.
It was also within 1,640ft of homes, in violation of laws that require a mile minimum distance.
On August 18, Xinhua quoted an unidentified executive from the company as saying: “The company has handled hazardous chemicals during a period without a license.”
The agency said documents showed the company was approved to handle hazardous chemicals between April and October last year.
Ruihai obtained a port operation license two months ago which again allowed it to work with toxic chemicals, Xinhua said.
Ten people, including Ruihai head Yu Xuewei and deputy head Dong Shexuan, were detained on August 13, state media reported.
China’s top prosecutor is reported to be investigating all involved officials for dereliction of duty and other crimes.
Doubts have also been cast on a consultation process Ruihai claims it had with residents, in which most respondents were said to have raised no objection to the company operating.
Meanwhile, heavy rain has hampered recovery efforts.
Experts expressed concern that rain could spread some of the vast quantities of hazardous material at the site or set off chemical reactions sparking further explosions.