Several officials in Tibet, including the county party secretary, were removed from office and more are under investigation, they said.

The studio run by renowned visual artist Cai Guoqiang set off 1,050 fireworks in a Tibetan mountain range last month to create a display resembling a dragon.

Orange puffs of smoke lingered in the air up to 5,020 metres (16,470 feet) above sea level in the western autonomous region's Gyantse County after the 52-second "Rising Dragon" show, investigators said in a statement shared by state broadcaster CCTV.

The show was sponsored by Chinese-owned outdoor equipment brand Arc'teryx and sparked a massive backlash on Chinese social media, with people accusing it of environmental ignorance.

Cai, the mastermind behind the fireworks display at the 2008 Beijing Olympics opening ceremony, later apologised for the damage.

He said there were "indeed many miscalculations" and accepted public criticism.

Arc'teryx, headquartered in Canada, also apologised.

Cai's studio is suspected of violating the Qinghai-Tibet Plateau Ecological Protection Law, investigators said.

"The report finds that the incident constitutes a human-induced disturbance in a high-altitude ecologically sensitive area," their statement said.

There was little short-term damage but ecological risks should be monitored, it said.

Authorities found that residue from the display had not been thoroughly cleared and that foot and vehicle traffic had damaged soil.

Sudden light and noise also disturbed wildlife.

The Tibetan city of Shigatse has also launched an assessment of ecological damage and restoration costs.

Both Cai's studio and Arc'teryx would be legally responsible to pay compensation, investigators said.

However, they gave no indication of any possible amount that would have to be paid.