  In this work, we search the OGLE-IV outer Galactic bulge fields for
short-period variable objects. The investigation focuses on unexplored
timescales roughly below one hour in an area containing about 700 million
stellar sources down to approximately I=20 mag. We concentrate mainly on Blue
Large-Amplitude Pulsators (BLAPs), which represent a recently discovered
enigmatic class of short-period hot subluminous stars. We find 33 BLAPs in the
period range from 7.5 to 66.5 min. Thirty-one of them are new discoveries,
which increases the number of known stars of this class to over one hundred.
Additional eighteen objects with pulsation-like light curve shapes and periods
ranging from 17.3 to 53.7 min are presented. Very likely, these are $\delta$
Sct/SX Phe-type stars, but some of them could be pulsating hot subdwarfs or
BLAPs. We also report on the detection of five eclipsing binary systems with
orbital periods between 61.2 and 121.9 min and three mysterious variable
objects with I-band amplitudes larger than 0.9 mag. A spectroscopic follow-up
would help in the final classification of the variables.
