The aftermath of the fire in a residential area of Nanjing, Jiangsu province, China, on February 23.
Hong Kong CNN  — 

At least 15 people were killed in a fire thought to have been started by an electric bicycle parked at a high-rise residential building in eastern China early Friday morning, state media have reported.

Forty-four people were also injured during the blaze that engulfed the 34-floor building in the eastern city of Nanjing, the media outlet CCTV said.

Two were in critical and serious condition while the rest suffered minor injuries, the state broadcaster reported, adding that all were hospitalized.

A preliminary investigation found an electric bike parked on an open floor of the building may have caught fire, according to the state broadcaster. Investigations are continuing.

Footage on Chinese social media showed a ball of fire spreading to the exterior of the building. Billows of smoke emerged from apartments on various floors, leaving burn marks on the facade of the building.

Authorities received calls for help at 4:39 a.m. and dispatched 20 fire engines to the scene, according to CCTV. The fire was put out at 6 a.m.

At a press conference early Saturday, Nanjing Mayor Chen Zhichang bowed to the public when he offered condolences and said he was “deeply sorry” to victims’ families and those who were injured, according to the Nanjing government’s official WeChat account.

He said officials were “deeply saddened” by the event, adding that an investigation is under way. “We will…give the victims and society an answer,” he said.

The blaze was a trending topic on the Chinese social media platform Weibo on Saturday, being viewed more than 470 million times by the afternoon.

Faulty electric bicycles have been reportedly linked to several blazes in the country in recent years.

Some commentators, including former Global Times editor-in-chief Hu Xijin, on Saturday called for stricter regulations on the increasingly popular form of transport.

“It’s really shocking and heartbreaking. How to manage electric bicycles is a major problem to tackle,” wrote Hu, who has 24 million followers on Weibo.

Some commentators called for the authorities to be more proactive.

“I don’t want to see leaders of a certain level apologize and bow after every major safety incident,” said one online commentator, with 179,000 followers.

“This kind of behavior won’t impress people these days as what everyone wishes to see is what they actually do for the people.”