  The smallest of the four detectors which claim to have observed neutrinos
from SN 1987a registered the events more than 4 h earlier than the other three
ones. This claim is not usually accepted because it is difficult to understand
that the other (and larger) detectors did not register any events at the same
time. It is shown that microlensing of the neutrinos by a star in-between the
supernova (SN) and Earth can enhance the neutrino intensity at the position of
one detector by more than an order of magnitude with respect to the other
detectors. Such a configuration is improbable but not impossible. Essential for
this enhancement is the small source diameter, of order 100 km. So if two
bursts of neutrinos were emitted by SN 1987a at a separation of about 4 h it
could be explained easily that the smallest detector observed the first burst
while the other ones missed it and vice versa.
