Beijing Youth Daily, a state-owned newspaper, reported that some residents said they saw explosives being thrown from the building, but a local official would not confirm those accounts.

In one video posted to social media, more than 15 blasts can be heard, and at least one was proceeded by an object falling through the air. Some explosions produced loud booms, while others were more modest, like fireworks.

In July, a man set off an explosion outside the United States Embassy in Beijing, badly injuring his hand. The police said he suffered from hallucinations and had been diagnosed with a paranoid personality disorder. A lighter, firecracker fragments and three unexploded firecrackers were found at the scene.