BEIJING (Reuters) - Chinese workers fled a high-rise office building on Friday after mysterious explosions in the northeastern city of Changchun, video posted on media showed, in what police have labeled a “criminal case”.

Reuters could not independently verify the video.

The city government said in a statement one person was killed in one of two explosions - one in the basement car park of the Wanda Plaza building, owned by Dalian Wanda Group, and one on the 30th floor - but did not give details.

The statement did not elaborate on the blasts or the motive and said merely that a criminal investigation was under way.

A spokesman for Wanda, a Chinese conglomerate with interests in property development and entertainment, told Reuters the group was aware of the situation but did not comment further.

Footage and images circulating on Twitter and Chinese social media platform Weibo showed people running from a building through white smoke, with one video showing a series of blasts in the same place at ground level, several seconds apart, as a crowd looked on.