All bottles contained in 20 cartons were found to be already date-expired.
The DAO had brought the mineral water of Maaibeni brand for inauguration of its new building on coming Saturday.
Secretary at the Ministry of Home Affairs, Surya Prasad Silwal, has been invited as the chief guest for the function.
Office’s staff had opened the cartons after they sensed some foul smell as soon as they stored the water inside a room of the Office.
Local Timalsena Stores of district headquarters Phidim had supplied the water to the DAO.
A DAO staffer Surendra Dahal said the bottles’ expiration date was October 2014.
Meanwhile, owner of the Stores, Prakash Timalsena said the incident was not intentional, but due a human error.
“A new staffer at my store mistook the cartons that were kept in a corner to return to the bottling company after the date expiry,” he said.
Chief District Officer (CDO) Pradeep Raj Kandel said the DAO will investigate into the case.
Earlier, mineral water bottled by the Ilam Spring Water Industries was banned for sale in July-August last year after the bottles were found containing inedible materials.
But after the authorities failed to produce any test report to prove the contamination for few months, the company resumed sale, according to a trader Santosh Shrestha.