  We present candidates for non-pulsating stars lying in the classical Cepheid
instability strip based on OGLE photometric maps combined with Str\"omgren
photometry obtained with the 4.1-m SOAR telescope, and Gaia DR2 data in four
fields in the Large Magellanic Cloud. We selected 19 candidates in total. After
analysis of their light curves from OGLE surveys we found that all these stars
appear to be photometrically stable at the level of a few mmag. Our results
show that non-pulsating stars might constitute to about 21%-30% of the whole
sample of giant stars located in the classical instability strip. Furthermore,
we identified potential candidates for classical Cepheids with hot companions
based on their Str\"omgren colours.
