  We investigate several mechanisms of vortex creation during splitting of a
spinor BEC in a magnetic trap controlled by a pair of current carrying wires
and bias magnetic fields. Our study is motivated by a recent MIT experiment on
splitting BECs with a similar trap, where unexpected fork-like structure
appeared in the interference fringes corresponding to interference of two
condensates, one with and the other without a singly quantized vortex. It is
well-known that in a spin-1 BEC in a quadrupole trap a doubly quantized vortex
is produced topologically by a ``slow'' reversal of bias magnetic field $B_z$.
We find that in the magnetic trap considered it is also possible to produce a
4- and 1-quantized vortex in a spin-1 BEC. The latter is possible, for example,
during the magnetic field switching-off process. We therefore provide a
possible explanation for the unexpected interference patterns in the
experiment. We also give an example of the creation of singly quantized
vortices due to ``fast'' splitting, which is a possible alternative mechanism
of the interference pattern.
