  A search for the decays Bs -> mu+ mu- and B0 -> mu+ mu- is performed with
0.37 fb^-1 of pp collisions at sqrt{s} = 7 TeV collected by the LHCb experiment
in 2011. The upper limits on the branching fractions are BR (Bs -> mu+ mu-) <
1.6 x 10^-8 and BR(B0 -> mu+ mu-) < 3.6 x 10^-9 at 95% confidence level. A
combination of these results with the LHCb limits obtained with the 2010
dataset leads to BR (Bs -> mu+ mu-) < 1.4 x 10^-8 and BR (B0 -> mu+ mu-) < 3.2
x 10^-9 at 95% confidence level.
