  Transitional discs are a class of circumstellar discs around young stars with
extensive clearing of dusty material within their inner regions on 10s of au
scales. One of the primary candidates for this kind of clearing is the
formation of planet(s) within the disc that then accrete or clear their
immediate area as they migrate through the disc.
  Our sample included eight transitional discs. Using the Keck/NIRC2 instrument
we utilised the Sparse Aperture Masking (SAM) interferometry technique to
search for asymmetries indicative of ongoing planet formation. We searched for
close-in companions using both model fitting and interferometric image
reconstruction techniques. Using simulated data, we derived diagnostics that
helped us to distinguish between point sources and extended asymmetric disc
emission. In addition, we investigated the degeneracy between the contrast and
separation that appear for marginally resolved companions.
  We found FP Tau to contain a previously unseen disc wall, and DM Tau, LkHa
330, and TW Hya to contain an asymmetric signal indicative of point source-like
emission.
  We placed upper limits on the contrast of a companion in RXJ1842.9-3532 and
V2246 Oph. We ruled the asymmetry signal in RXJ1615.3-3255 and V2062 Oph to be
false positives.
  In the cases where our data indicated a potential companion we computed
estimates for the value of $M_c \dot M_c$ and found values in the range of
$10^{-5} - 10^{-3} M^2_J yr^{-1}$.
  We found significant asymmetries in four targets. Of these, three were
consistent with companions. We resolved a previously unseen gap in the disc of
FP Tau extending inwards from approximately 10 au.
