It's imperative that you seriously plan for disaster, whether man-made or natural. A little effort in preparing for a range of potential threats will go a long way in the recovery of your business and your ability to quickly rebound and serve customers' needs in a time of crisis.
The excellent Red Cross site offers specific instructions and suggestions for businesses as well as families. This site considers not only the physical damage to life and property that can occur, but the significant financial and operating realities in the aftermath of an upheaval. Planning can avoid many of these problems.
One of the most important things you can do in an emergency is to have only one individual authorized to dispense information to the public, the press, customers and vendors.
This is what saved the manufacturer in the still-unsolved Tylenol-poisoning case some years back. The Public Relations Department (now usually called Corporate Communications) was well prepared, knew the policy on product disasters, knew what to say, but much more importantly knew what not to say. Their training and honest communication skills saved the day.