  The Optical Gravitational Lensing Experiment (OGLE) is a great source of
top-quality photometry of classical pulsators. Collection of variable stars
from the fourth part of the project contains more than 38 000 RR Lyrae stars.
These stars pulsate mostly in the radial fundamental mode (RRab), in radial
first overtone (RRc) or in both modes simultaneously (RRd). Analysis of the
OGLE data allowed to detect additional non-radial modes in RRc and in RRd
stars. We have found more than 260 double-mode stars with characteristic period
ratio of the additional (shorter) period to first overtone period around 0.61,
increasing the number of known stars of this type by factor of 10. Stars from
the OGLE sample form three nearly parallel sequences in the Petersen diagram.
Some stars show more than one non-radial mode simultaneously. These modes
belong to different sequences.
