Massive piles of seaweed have washed ashore along Sierra Leone's coastline, covering the white sand and raising fears for tourism and the fishing industry, officials said Monday.
"People should stay away until we determine through lab tests whether the weeds are toxic and harmful to human beings. We are now turning people away from the area," warned Momodu Bah of the country's Environmental Protection Agency.
About 15 miles (24 kilometres) of beach is affected.
Residents and hotel owners along the 4km-long Lumley Beach in the west of Freetown said they were startled by the appearance of the thick brown seaweed which started washing up early Sunday and by late Monday stretched across the beach, covering every inch of sand.
Bah said scientists from the Institute of Marine Biology and Oceanography had taken samples for laboratory tests.
"We are now working to identify the source and whether it is as a result of a seismic survey for oil and gas exploration as Sierra Leone is within the West African Maritime eco-region and shares a border with Liberia where drilling for oil is also going on," he said.
"Another likely cause could be dredging being undertaken by mining companies or dumping of trash by international shipping vessels but we don't have sure answers for now."
Bah raised concerns for marine life, including turtles who breed in the area.
The National Tourist Board's planning and production development manager, Umaru Woodie, said "clearing the beach is an herculean task" and hotel guests were complaining about the smell.
Fisherman Tommy Koroma added: "The magnitude of the weeds is alarming ... We have not ventured out to sea as our nets are clogged up."
Explore further: Claim: Wet sand causes digestion problems