Warne claimed two for 27 but 36-year-old Mascarenhas went one better as Durham were bowled out for 128 at the Rose Bowl.
Hampshire were 195 for five in reply at stumps.
Pakistan's Azhar Mahmood hit a battling 84 to rescue Surrey against champions Sussex at The Oval.
Mahmood played a vital role after Surrey had been reduced to 84 for five with the home side eventually reaching 304 all out.
Robin Martin-Jenkins was the pick of the Sussex bowlers taking four for 59.
Openers Ian Ward and Richard Montgomerie were untroubled as they took Sussex to 75-0 at stumps.
Lancashire, one of the favourites for the County championship, made 306 for four away at Northamptonshire with centuries from Iain Sutcliffe and Aussie star Stuart Law.
Law hit 108 off 152 balls before falling to Johann Louw - who finished the day with three wickets - while Sutcliffe made more mundane progress in constructing 104 off 253 before he was dismissed by Graeme Swann.
Kent paceman Martin Saggers took three for 18 as Gloucestershire slumped to 140 for five before rain brough an early close at Bristol.