Maggie Cheung injured her head during filming and had too be doubled for parts of the film. The double can be seen in long shots and spends most of the time with the back of her head too the camera.
Jackie considers this his safest movie. Injury wise.
Some versions of the film miss out the following scenes:
1.The opening scene with the trucks.
2. Bill Tung farting in the elavator.
3. Ka Kui hiding under the table too plant the bug.
4. May having a flashback of Ka Kui pulling her off her scooter in PS1.
Filming on a low budget, they could not afford too clear the main road so they filmed illegally. Most of the cars, when Jackie runs recklessly across are real. The stunt car is the car that hits Jackie. It was only meant too stop in front of him but Jackie left it in.
The explosion at the end was the biggest one in a HK film at that time.
Ken Lo plays a fireman at the mall.
The literal title of this film is Police Story Sequel.