empty cells not empty according to excel

Hi!

I have an excel sheet that has values from A1:O2000. When I press ctrl+end to have excel tell me where the end of the sheet is it goes to cell S2000 even though Columns P:S are empty. I used to have some data here but it has been deleted. How do I "really" clear the cells so that when I press crtl+end it points to O2000?

I have tried deleting all columns to the right of column O and also clear contents.

This is an issue as I import the excel sheet to Matlab where Matlab sees these empty columns (P:S) as NaN.

Any help is much appreciated,

Regards,
Kbka

Done that. Still same issue.