  We consider a continuous-time branching random walk on $\mathbb{Z}$ in a
random non homogeneous environment. Particles can walk on the lattice points or
disappear with random intensities. The process starts with one particle at
initial time $t=0$. It can walk on the lattice points or disappear with a
random intensity until it reach the point, where initial particle can split
into two offspring. This lattice point we call reproduction source. The
offspring of the initial particle evolve according to the same law,
independently of each other and the entire prehistory. The aim of the paper is
to study the conditions for the presence of exponential growth of the average
number of particle at an every lattice point. For this purpose we investigate
the spectrum of the random evolution operator of the average particle numbers.
We derive the condition under which there is exponential growth with
probability one. We also study the process under the violation of this
condition and present the lower and upper estimates for the probability of
exponential growth.
