That's one gaint gas leak.
Shanghai is a city in China.
Revenge of The Fallen film
The city Shanghai is evacuated after a gas leak. What the people of Shanghai don't know is that this was made up because of the real danger: Decepticons.
A new team of advanced Autobots is send to Shanghai to stop the Decepticons, together with a team called N.E.S.T.. After the NEST team lands and investigates an area, a nearby vehicle reveals his true form, being the gigantic decepticon Demolishor. After smacking down some choppers the Decepticon races away. At the same time another Decepticon, the coward Sideways races away, trying to flight from the Autobots. With the two decepticons on the run, Sidewipe, The twins, and The Arcee Twins/Triplets go after them. Sideswipe suceeds to defeat Sideways (while Sideways is in vehicle form!). Optimus and Ironhide attack Demolishor and stop him. He says that 'The Fallen shall rise again'(Those were his last words).
Later, at the Autobot base, Theodore Galloway says that the Autobots made a mess of Shanghai, but it was really Demolishor driving into the road that caused the damage.
We don't wonder where Sideways is.
Revenge of the fallen game
Multiple missions are in Shanghai, in the Decepticon as the in the Autobot campaign.