  We report long, pointed ROSAT HRI observations of the hyperluminous galaxies
IRAS F00235+1024, F12514+1027, F14481+4454 and F14537+1950. Two of them are
optically classified as Seyfert-like. No X-ray sources are detected at the
positions of any of the objects, with a mean upper limit L(X)/L(Bol) of 2.3
times 10^-4. This indicates that any active nuclei are either atypically weak
at X-ray wavelengths or obscured by column densities N(H)>10^23 cm^-2. They
differ markedly from `ordinary' Seyfert 2 galaxies, bearing a closer
resemblance in the soft X-ray band to composite Seyfert 2 galaxies or to some
types of starburst.
