The Bulls and SA Rugby have reportedly received an official letter demanding an explanation for why the Pretoria outfit fielded a weakened side in their Champions Cup quarter-final.
Northampton advanced to the Champions Cup semi-finals on Saturday, after beating the Bulls 59-22 at Franklin's Gardens.
The Bulls reached the quarter-finals of the Champions Cup for the first time ever after they thrashed Lyon 59-19 in Pretoria on Saturday.
Jake White says his Bulls players must learn from the defeat and accept the result after suffering a tough loss against a hugely experienced Leinster side in Ireland.
Player-of-the-match Jack Conan was one of five second-half try scorers for Leinster in a dominant 47-14 United Rugby Championship (URC) win over the Bulls at the RDS.
The Bulls have made six changes - including welcoming back star back-rower Elrigh Louw - for Saturday's massive URC clash against table-topping Leinster in Ireland.