Searching more than 1000 records

I have created this function to get an array of the item list.

var returnCols = [];
returnCols[0] = new nlobjSearchColumn('name');
returnCols[1] = new nlobjSearchColumn('description');
returnCols[2] = new nlobjSearchColumn('manufacturer');
returnCols[3] = new nlobjSearchColumn('price');
returnCols[4] = new nlobjSearchColumn('cost');
itemList = nlapiSearchRecord('item', null, null, returnCols);


However, it is only returning 1000 items and I need it to return the entire collection of items.

The array of items is needed to construct a list of manufacturers as well as a custom built search plugin. (one which allows searching by manufacturer by clicking on a manufacturer in the list).

The search plugin is working except now that there are over 1000 items in the inventory, the plugin can only see the first 1000.