According to captain Rui Pereira da Terra from the Cascais Port, after following advice from health authorities and thanks to a change in weather conditions, the green flag can now be raised on the beaches.

"The algae is normal in appearance and is known for recurring in the area. It is not to be confused with what happened on the Algarve coast during the past week and does not represent a public health hazard," said Pereira da Terra.

According to the official, the red flags were hoisted on Thursday as a "precautionary measure" and are still present in small areas of Carcavelos beach mainly "because of the inconvenience that could potentially be caused by such high concentrations of algae in the ocean and on the sand”.

"Because the weather conditions are already different today, concentrations of the algae are already subsiding and it does not represent a danger to public health.”

Captain Pereira da Terra also explained that the algae detected on the Cascais beaches have no relation to the microalgae detected in the Algarve, stressing that similar phenomena occur year round due to sea currents in the local area.