  We present the results of the optical follow-up, conducted by the TOROS
collaboration, of gravitational wave events detected during the Advanced
LIGO-Virgo second observing run (Nov 2016 -- Aug 2017). Given the limited field
of view ($\sim100\arcmin$) of our observational instrumentation we targeted
galaxies within the area of high localization probability that were observable
from our sites. We analyzed the observations using difference imaging, followed
by a Random Forest algorithm to discriminate between real and bogus transients.
For all three events that we respond to, except GW170817, we did not find any
bona fide optical transient that was plausibly linked with the observed
gravitational wave event. Our observations were conducted using telescopes at
Estaci\'{o}n Astrof\'{\i}sica de Bosque Alegre, Cerro Tololo Inter-American
Observatory, and the Dr. Cristina V. Torres Memorial Astronomical Observatory.
Our results are consistent with the LIGO-Virgo detections of a binary black
hole merger (GW170104) for which no electromagnetic counterparts were expected,
as well as a binary neutron star merger (GW170817) for which an optical
transient was found as expected.
