  In this talk latest results from the analysis of e+e- pairs emitted in Pb+Au
collisions at 40 AGeV/c and a combined analysis of all data available at 158
AGeV/c are presented. The enhancement of low-mass e+e- pairs (m_ee>0.2 GeV/c^2)
with respect to the expected yield from hadron decays first reported at 158
AGeV/c is also found at 40 AGeV/c and is even larger there. Comparing to
various theoretical models based on pi-pi-annihilation, the data can only be
reproduced, if the properties of the intermediate rho in the hot and dense
medium are modified. Theoretically, the modification is linked to baryon
density rather than temperature. Constraints from hadron data taken at the same
beam energies indeed indicate a fireball evolution along a trajectory of higher
baryon density at 40 AGeV/c, consistent with the observed larger enhancement
factor.
