No one knows for certain what happened, but it's a fair bet that it was not an accident.
没有人知道究竟发生了什么,但几乎可以肯定这并非意外。
The city was equipped with a drainage system, for a great many clay pipes were found beneath the narrow streets.
城里甚至还敷设了排水系统,因为在狭窄的街道底下发现了许许多多陶土制作的排水管道。