  For a slim, planar, semimodular lattice, G. Cz\'edli and E.\,T. Schmidt
introduced the fork extension in 2012. In this note we prove that the fork
extension has the Congruence Extension Property. This paper has been merged
with Part II, under the title Congruences of fork extensions of slim
semimodular lattices, see arXiv: 1307.8404
