Mepa has called in the police after finding evidence that somebody was cutting rock in order to widen the natural cliff tunnel into the scenic 'inland sea' in Gozo.
The authority said that last week it started investigating a report that rock cutting was being carried out inside the area which leads to the inland sea at Dwejra.
Preliminary investigations indicated that explosive material was probably used.
"Given the nature of the case, Mepa reported the case to the police for any necessary action from their end. The authority is informed that a magisterial inquiry is underway."
The archway which links the marine environment of the Dwejra coastal area to the inland lagoon is a popular tourist attraction used by boats which tour the nearby cliffs including the Fungus Rock and the Azure Window.