One individual has been placed under residential surveillance while 25 officials are facing disciplinary action as a result of a deadly fire caused by an illegally modified electric bicycle, which claimed eight lives in Kunming in China's Yunnan province, authorities announced on Wednesday.

The announcement was made along with the release of the official investigation findings into the April 12 blaze at a motorcycle parts store in the Chenggong district of the city. Along with the eight deaths, the fire resulted in direct economic losses of 530,400 yuan ($75,839).

A provincial government investigation team concluded that the fire was a non-production safety accident, with the direct cause being the short-circuiting and ignition of a modified battery on an e-bike that was being charged on the premises. Contributing factors included the illegal conversion of the shop's second floor into a living space, the use and modification of a non-compliant e-bike, the unauthorized alteration of its battery, and inadequate oversight by relevant departments and other entities.

The investigation found that Yan Cai, the shop's operator, had illegally converted the second floor into residential quarters. On the night of the fire, nine individuals, including Yan's family members and visiting relatives, were staying inside. All eight victims were found on the second floor.

The report stated that, to extend the relevant e-bike's range and increase speed, Yan illegally replaced and added large-capacity lead-acid and lithium batteries, modifying the battery compartment and compromising the vehicle's original electrical safety design. The lithium battery pack had previously shown signs of failure, including swelling.

On the night of April 11, after charging the modified e-bike on the shop's first floor — an area also cluttered with motorcycle parts and other flammable materials — Yan went to sleep. The fire started around 1:50 am on April 12. As the first floor, functioning as a sales area, and the second-floor living space were connected only by an ordinary staircase without fire safety separation, toxic smoke and flames rapidly spread upward, blocking the escape route. Most of the victims were elderly, women or children.

Deemed primarily responsible, Yan is suspected of the crime of causing a fire by negligence and has been placed under residential surveillance by police, with the prospect of further legal action.

He Wenjuan, the owner of the property, is also facing proceedings for including a provision in the contract explicitly permitting the space to be used for both "business and residential" purposes without obtaining approval from the relevant authorities. This unauthorized clause facilitated the illegal change in the building’s designated use. He also failed to ensure the installation of mandatory physical fire separations or a separate evacuation staircase between the commercial area and the residential living quarters within the property.

In addition, the investigation found that the company which sold Yan the substandard and reportedly swollen battery, failed in its product safety responsibilities.

A total of 25 individuals from 10 entities, including the Chenggong district government, have been recommended for accountability and disciplinary action for deficiencies in the performance of duties.