New Delhi, Feb. 27 -- A toxic algae bloom known as a red tide is causing the mass deaths of crayfish and other ocean life on parts of South Africa's west coast.

The environment ministry warned people on Thursday against collecting and eating the crayfish, which could be toxic, and police were deployed on some beaches.

A red tide occurs when colonies of algae in the ocean grow out of control, according to the U.S. government's National Ocean Service. The algae give the seawater a distinct reddish tinge, and produce toxins that kill fish and shellfish.

It's a reasonably common happening in South African coastal areas, but this week's red tide was an especially severe one, according to South Africa's Ministry of Forestry, Fisheries and th...