  The KM3NeT Collaboration is constructing two deep-sea Cherenkov detectors in
the Mediterranean Sea. The ARCA detector aims at TeV-PeV neutrino astronomy,
while the ORCA detector is optimised for atmospheric neutrino oscillation
studies at energies of a few GeV. In this contribution, an analysis of the data
collected with the first deployed detection units of the ARCA detector is
presented. A high-purity sample of atmospheric neutrinos is selected
demonstrating the capability of the ARCA detector.
