Update: Thanks to Brian we have more pictures and another video. The pictures are from this afternoon from filming with the Rally Fighter (description below). The video shows Mark Wahlberg, Jack Reynor, Nicola Peltz and TJ Miller running from the smoking Sonic Racer.
Update 2: The warehouse location has been ID'ed as the Fisher Body Plant. To view another video of the explosions set off by "explosives hung on ropes diagonally across the front of the building" then click here.
Transformers 4 production was filming this afternoon at the Russell Bazaar location in Detroit. I spotted a helicopter mounted with a camera, the Rally Fighter vehicle, Sonic RS Rally Car and two Cadillac Escalades. The Escalades had US Gov plates and soldiers with guns in them. The Rally Fighter was chasing one of the Sonics, with the ESQ's running behind and with the Rally Fighter. They did this scene over and over. The helicopter was diving at them and flying through the buildings chasing them as it filmed. The Helo was on station from at least 2 pm (from seeing it in the distance. I got there at around 6pm) till about 6:30 then it went to film across the freeway at second location. They then changed their location across I-75 from the Bazaar to the intersection of Harper and St. Antoine with the crew and copper.
At the warehouse at Harper and St. Antoine around 7:15pm they set off a massive explosion at the warehouse with the camcopter and Porsche filming. About a half hour later they set up a shot with Mark Wahlberg, Jack Reynor, Nicola Peltz, and T.J. Miller running from the Chevy Sonic shouting to each other while the car was smoking next to the warehouse. While they were setting up that shot the flat nosed rusted semi character was brought up to the set and looked like it was going to be used in the next scene.