Experts are examining the remains of an old wall which could possibly have formed part of the original Fort St Elmo before the Great Siege.
The discovery was made late last month during restoration works on the upper part of the fort.
Historian Stephen Spiteri said that during the restoration works, a stone came loose and workers then discovered the remains of an ancient wall behind it. Further excavation will be necessary, but it could be that the wall led to a tunnel to Grand Harbour from where men and material were smuggled when the fort was besieged during the Great Siege of 1565.
Architect Ray Demicoli said the wall went down to the rock and indicated how deep the original ditch was.
The wall is believed to have been built in 1552.Other remains of the original fort exist and form part of the present structure.
Dr Spiteri said experts had long suspected that remains of the original fort still remained and a trench was dug some time ago just a few metres away from where the old wall was found. However no new remains were found.
Minister Austin Gatt, who visited Fort St Elmo this morning, said that in view of the importance of this discovery and the need for further excavations, completion of restoration of the upper part of Fort St Elmo may extend beyond the end of 2014.