  A spectral line image cube generated from 115 minutes of MWA data that covers
a field of view of 400 sq. deg. around the Galactic Centre is used to perform
the first Search for ExtraTerrestrial Intelligence (SETI) with the Murchison
Widefield Array. Our work constitutes the first modern SETI experiment at low
radio frequencies, here between 103 and 133 MHz, paving the way for large-scale
searches with the MWA and, in the future, the low frequency Square Kilometre
Array. Limits of a few hundred mJy/beam for narrow band emission (10 kHz) are
derived from our data, across our 400 sq. deg. field of view. Within this
field, 45 exoplanets in 38 planetary systems are known. We extract spectra at
the locations of these systems from our image cube, to place limits on the
presence of narrow line emission from these systems. We then derive minimum
isotropic transmitter powers for these exoplanets; a small handful of the
closest objects (10s of pc) yield our best limits of order $10^{14}$ W
(Equivalent Isotropic Radiated Power: EIRP). These limits lie above the highest
power directional transmitters near these frequencies currently operational on
Earth. A SETI experiment with the MWA covering the full accessible sky and its
full frequency range would require approximately one month of observing time.
The MWA frequency range, its Southern Hemisphere location on an extraordinarily
radio quiet site, its very large field of view, and its high sensitivity make
it a unique facility for SETI.
