More than 30 people have fallen sick and four have died in Guatemala after eating shellfish.
The National Commission for the Surveillance and Control of Red Tide in Guatemala has extended an alert because of the presence of saxitoxins above the limits on the coasts of Tiquisate, Escuintla, Retalhuleu and San Marcos.
Public health officials said that since the end of April, 34 people had been affected and three children and one adult had died.
Authorities urged the public not to eat bivalve mollusks such as mussels, clams and oysters.
A warning was issued earlier this month after monitoring and analysis detected high concentrations of saxitoxins above the limits.
Saxitoxin is a toxin responsible for paralytic shellfish poisoning (PSP). Harmful algal blooms are often called red tides.