Dye illegally dumped by a factory is apparently responsible for turning the Beirut River an eerie shade of blood red.
An investigation began last week after the river, which separates the eastern and western suburbs of Beirut, turned a deep red, prompting fears there had been a mass dump from a slaughterhouse.
The river, which flows into the Mediterranean, was visited by government and local officials, with preliminary test indicating dye to be the culprit, the Daily Star said.
According to officials at Beirut's Environment Ministry the contamination has been traced back to a factory in either nearby Hazmieh or Baabda.
Further analysis is being conducted on the substance by the American University of Beirut, Zawya.com reported, but there are fears the incident could have catastrophic effects on the local ecosystem if the substance is identified as industrial.
Tests are expected to conclude next week.
Industry Minister Vrej Sabounjian said strict measures will be taken against the party responsible for releasing the substance into the river.
He said: "There are guidelines and conditions for all registered industries in the country to abide by ... A failure to respect these conditions will not be tolerated."
Once part of an urban development project, the Beirut River is increasingly becoming a dumping ground for sewage and waste, said the Daily Star.