Massive limestone blocks dating back to Roman times have been unearthed during excavation works near Jetties Wharf and the Galizia canal in Marsa.
The Malta Environment and Planning Authority yesterday morning stopped the works as soon as its enforcement officers became aware of the discovery.
The excavation works are meant to provide a channel for rainwater to avoid flooding. They are being carried out by the Ministry for Resources and Infrastructure.
The authority said that although an application for a development permit had been filed by the ministry, no permit had so far been issued.
Mepa officers and representatives of the Superintendence of Cultural Heritage who went on site noted "large blocks from Roman warehouses". The blocks measure 120 cm x 60 cm x 60cm.
A Mepa spokesman said the area is archaeologically sensitive. One had to remember that the coastline in ancient times was not as it is today.
"Mepa will be doing its utmost to ensure the safety of the country's cultural heritage," the spokesman added.
In 1647, historian Gian Frangisk Abela had cited the existence of Roman warehouses in the area. The remains spotted today are likely to be the same as those documented in the Museums Department's annual reports of the 1940s and 1950s.
A 1957 report on finds in the same area had been compiled by Charles Zammit, former curator of the Museums Department and son of the renowned archaeologist Temi Zammit. He had noted that the storage jars and amphorae that were found indicated domestic and commercial activity.
According to Mr Zammit, the remains dated back to classical and mediaeval times. The author also mentioned the presence of large rectangular rooms and an enclosure, pointing out the high quality of the masonry.
When contacted, Anthony Pace, Superintendent of Cultural Heritage, said the superintendence will be working closely with the ministry's architect to find out how far the remains extended. He said they could well go further inland under part of a football pitch of the school nearby.
The superintendence has conducted two inspections, one with Mepa officials.
"I am particularly concerned about these works because of the richness of cultural heritage that the site presents including the canal itself. The richness of the area has been evident for a long time. In 1993 I had directed excavations close to the power station about 500 metres away where remains of a mediaeval chapel and cemetery were unearthed," Dr Pace said.
When contacted Timmy Gambin whose specialisation is ports from the ancient period to the Middle Ages said Marsa was an extremely important Roman port.
In the 1760s, a huge Roman warehouse complex was discovered in Jesuits Hill under the power station. In the 1950s another complex was found near Racecourse Street while in 1956, yet another large complex came to light under the Marsa school where the current excavations are taking place.
"This widespread complex of warehouses clearly indicates that the Roman port did not cater solely for the local population which then numbered between 12,000 and 20,000.
"The Romans built these harbours as part of a network of havens for the transport of grain from North Africa to Rome. These were free ports known as emporiums," Mr Gambin added.
The remains of such ports are of international importance and scholars around the Mediterranean in particular would be greatly interested to study them, he said.