Panaji, April 19 (IANS) A fresh wave of tar balls have reappeared on Goa's beaches, layering the sand with oily streaks.

The problem is back, more than six months after tar balls floating in from the sea layered the state's famed beaches.

The beaches of Varca-Benaulim, about 40 km from here, were Monday evening streaked by the oily residue.

According to marine scientists, the messy tar balls are generated after sea-going ships discharge burnt-oil into the sea off the coast, resulting in large quantities of semi-solid oil lumps,

Tourism Director Swapnil Naik said there was "no confirmation as yet on the source of the tar balls".

"Cleaning personnel and government agencies have started the clean-up operation of tar balls which have appeared along the affected beaches over the last 24 hours. The beaches should be free of tar balls soon," Naik told IANS.

When asked about long term measures to ensure that the tar ball phenomenon - which last year threatened to ruin Goa's tourist season after wave after wave of tar balls layered several of Goa's beaches in September 2010 - doesn't repeat itself, Naik said the government was trying to identify the ships responsible.

"We are in the process of contacting the Indian Coast Guard to give us a list of ships operating along the coast. The same will be shared with (Nagpur-based) National Environmental Engineering Research Institute (NEERI) along with samples of the tar balls to ascertain if they are from ships operating in the coastal waters".

"We will also consult with the National Institute of Oceanography on the occurrence. Additionally, the Goa Coastal Zone Management Authority will also be taking up the matter with the central government agency in Delhi," the official said.