The fluorescence detector (FD) of the Pierre Auger Observatory is sensitive to upward-going air showers for energies above 10^17 eV. Given its operation time and wide field of view, the FD has the potential to support or constrain the recent "anomalous" observations by the ANITA detector, interpreted as upward-going air showers of unexplained nature.
We have used 14 years of data collected by the FD to search for upward-going showers using a set of quality selection criteria defined using 10% of the full data sample.
To distinguish candidates from false positives, calculate the exposure and obtain the expected background, dedicated simulations for signal (upward-going events) and background (downward-going events) have been performed.
Results of the analysis after unblinding the data set are presented.
Finally, the exposure and sensitivity for the specific scenario of a signal being ascribed to tau lepton decay are calculated and the corresponding upper limits are shown as a function of primary energy and in different zenith angle ranges.