Stores containing fish farming equipment were destroyed by fire early this morning at Triq il-Kappella ta' Sta Marija, limits of Maghtab.
Several fire engines were deployed to the scene to fight the fierce blaze at about 2.30 a.m. The operation continued for several hours.
The damage, said to run into thousands of euro, included nets and tuna pens.
No one was injured.
Magistrate Lawrence Quintano is holding an inquiry