BL Lacertae are sources of the observed ultra-high energy cosmic rays

We calculate angular correlation function between ultra-high energy cosmic rays (UHECR) observed by Yakutsk and AGASA experiments, and most powerful BL Lacertae objects (quasars with jets directed along the line of sight). We find significant correlation at 2.5 degrees with the probability of chance coincidence 2 x 10^{-5} and conclude that some of BL Lacertae are sources of the observed UHECR. We also see correlations at 10 degrees with the probability of coincidence 3 x 10^{-4}. A natural interpretation of this result is the existence of neutral and charged components of cosmic rays at highest energies, with charged primaries being deflected in extragalactic magnetic fields (EGMF) by an angle of order 10 degrees. The magnitude of EGMF deduced from here is of order 10^{-9} G assuming correlation length 1 Mpc.