The source of an oil spill which spread through Marsaxlokk Harbour and Birżebbuġa on Wednesday and yesterday has not yet been identified.

Transport Malta yesterday said it was investigating the cause.

“At this stage, no local source of pollution could be identified and thus the authority itself had to take immediate action to start clean-up operations and to remove scattered patches of heavy oil in the contaminated areas, particularly in the fairway, by the jetties, the coastline and around the Freeport Terminals and oil tanking areas,” Transport Malta said in a statement.

The clean-up operation is being coordinated by the authority’s officials and is still ongoing.  Some vessels’ hulls at Malta Freeport Terminals were contaminated and will have to be cleaned before their departure to ensure no further spread of pollution.

Birżebbuġa resident Frank Attard said he first noticed the oil spill on Wednesday at around 1pm. “There was the large brown patch all over Pretty Bay and Wied il-Buni,” he told Times of Malta. “The sand and rocks were also marred by oil patches. We informed the police and the local council.”

Yesterday, the oil was being cleaned up and he spotted officials giving tourists pieces of cloth to clean their oil-smeared feet. Meanwhile, marine biologist Alan Deidun explained to Times of Malta that the extent of the damage depended on whether the oil consisted of light or heavy components.

“The former has a lighter impact because it can evaporate,” he said.

“But unrefined, crude oil can have a much heavier impact because the oil can sink towards the bottom of the sea, clogging and smothering marine wildlife and organisms.”

The fact that the oil spill reached the sand was bad news, Dr Deidun said.

The sand particle size of Pretty Bay was very fine, unlike the coarse type found in bays such as Għajn Tuffieħa. Oil would easily cling to fine sand, making removal much more difficult.

“Probably they would need to remove most portions of sand – and we know that sand is quite rare in Malta,” said Dr Deidun.

“It’s not much solace but at least, the oil spill occurred in an area where the environment is already degraded, because of dredging. God forbid such a spill occurred in a more environmentally pristine area.”