A Chinese Foreign Ministry Spokesperson did promote the conspiracy on social media without any official report or evidence to back it.
30th Foreign Ministry Spokesperson Geng Shuang addressed a press conference on 13 March 2020 where he was asked about the suspicion on the U.S. Army. He answered that question by saying that the origin of the virus could only be determined by science and that it required professional and science-based assessment.
There have been no official reports of any such activity from the U.S. which could've caused the outbreak in China.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19 including symptoms, prevention and available treatment, please refer to the World Health Organisation or your national healthcare authority.