MANX Gas engineers have said they believe they have located and isolated the gas escape at the Isle of Man Bank in Regent Street, Douglas.
Yesterday the bank was evacuated and closed after a leak was reported.
Robert Gardner, engineering manager, said: "As soon as we have vented the building of any residual gas and can then verify there is no other source of escaping gas we are hopeful staff will be able to reoccupy the building later today.
"We will also be reinstating the area which had to be excavated to trace the source of the escape."
Manx Gas said it will only allow the bank to be re-opened once engineers are sure that the gas escape has been totally isolated so that it is safe for staff and customers to re-enter the building.