At least 20 people were injured, five of whom are still in serious condition, when an explosion rocked a residential complex in Mianyang City, southwest China's Sichuan Province, on Friday. 

The suspect, surnamed Xu, is also among the seriously injured and is in custody, local police confirmed in a statement on Friday.

The explosion occurred at around 11:30 a.m. local time (3:30 GMT). The motive for the crime is unclear.

The injured were taken to the hospital, and the investigation continues.