We present the results of a magnetic survey with FORS 1 in polarimetric mode of a sample of B and Herbig Ae stars with previously undetected magnetic fields .
For the first time a mean longitudinal magnetic field at a level higher than 3 \sigma has been detected in one normal B star , two HgMn stars , one PGa star and four SPB stars .
The observations of the three Herbig Ae stars ( also known as Vega-like stars ) reveal a definite longitudinal magnetic field in the star HD 139614 at 4.8 \sigma level : \left < { \cal B } _ { z } \right > = - 450 \pm 93 G. This is the largest magnetic field ever diagnosed for a Herbig Ae star .
A hint of a magnetic field is found in the other two stars , HD 144432 and HD 144668 , for which magnetic fields are measured at the \sim 1.6 \sigma and \sim 2.5 \sigma level respectively .