Liberian authorities say they are returning to Greece four shipping containers stuffed with tonnes of hazardous polyethylene waste bags that had been smuggled into Liberia "under the pretext of being recyclable materials".Anti-smuggling officers raised the alarm at the port of Monrovia when containers arrived "oozing some odour", says Environment Protect Agency (EPA) head Nathaniel Blama, and investigation followed.After analysis, the EPA said this particular type of plastic bags were banned from being recycled or re-used in Greece. It believes the bags were sold to a local waste dealer who in turn shipped them to Liberia.Liberia’s 350-mile coastline is largely underpatrolled and international fishing vessels often operate in its waters illegally.