2D arrays using NSMutableArray

I need to create a mutable two-dimensional array in Objective-C.

For example I have:

NSMutableArray *sections;
NSMutableArray *rows;

Each item in sections consists of an array rows. rows is an array that contains objects.

And I want to do something like this:

[ sections[i] addObject: objectToAdd]; //I want to add a new row

In order have something like this: section 0, rows: obj1, obj2, obj3 section 1, rows: obj4, obj5, obj6, obj 7...

Is there a way to do that in Objective-C?