  A search for second and third generation scalar and vector leptoquarks
produced in ep collisions via the lepton flavour violating processes ep to mu-X
and ep to tau-X is performed by the H1 Collaboration at HERA. The full H1 ep
data sample taken at a centre-of-mass energy of 319 GeV is used for the
analysis, corresponding to an integrated luminosity of 411 pb^-1. No evidence
for the production of such leptoquarks is observed in the H1 data. Leptoquarks
produced in ep collisions with a coupling strength of lambda=0.3 and decaying
with the same coupling strength to a muon-quark pair or a tau-quark pair are
excluded at 95% confidence level up to leptoquark masses of 712 GeV and 479
GeV, respectively.
