CAIRO - Average yields at an auction of 5.5 billion Egyptian pounds in domestic treasury bills rose on Sunday, and not all the bills initially offered were sold, the central bank said. Traders said demand for Egyptian treasury bills, especially by foreign investors, had tumbled since the protests that ousted President Hosni Mubarak erupted on January 25. The central bank sold only 3 billion pounds of 273-day T-bills after having originally offered 3.5 billion pounds. The average yield jumped to 12.162 per cent from 11.657 per cent at the last auction on Feb 7. The central bank sold all 2 billion pounds in 91-day T-bills it offered, with the average yield climbing to 11.097 per cent from 10.941 per cent at an auction last week.