  OH masers at 1720 MHz have proven to be excellent indicators of interactions
between supernova remnants and molecular clouds. OH excitation calculations
suggest that the 6049 MHz OH maser line is excited for higher column densities
than for the 1720 MHz line. Previous observations and modelling of 1612, 1665
and 1667 MHz OH absorption and 1720 MHz OH masers indicated that the column
densities in some supernova remnants, ~1e17 cm^-2, may be high enough for 6049
MHz OH masers to exist. It is therefore a potentially valuable indicator of
remnant-cloud interaction.
  We present excitation calculations predicting the formation of 6049 MHz OH
masers and results of a survey using the Parkes Methanol Multibeam receiver for
6049, 6035 and 6030 MHz OH masers towards 35 supernova remnants, a star-forming
region and 4 fields in the Large and Small Magellanic Clouds.
  Two new sites of 6035 and 6030 MHz OH maser emission associated with
star-forming regions have been discovered, but no 6049 MHz masers were detected
to a brightness temperature limit of ~0.3-0.6 K, even though modelling of the
OH excitation suggests that maser emission should have been detected. Our
upper-limits indicate that the OH column density for a typical remnant is less
than 1e16.4 cm^-2, which conflicts with observed and modelled column densities.
One possible explanation is that 6049 MHz OH masers may be more sensitive to
velocity coherence than 1720 MHz OH masers under some conditions.
