Tonnes of dead fish - level 3
Hundreds and thousands of dead fish have taken over the shores of Mexico's Cajititlan Lagoon over the past week.
Sparking an investigation into local wastewater treatment plants thought to be responsible, nearly 50 tonnes of popchoe chub freshwater fish have been removed from the lagoon in the past two days.
With numbers expected to increase in the coming days, the leader of the fishermen's co-operative in the area said the mass fish death was caused by high levels of pollution at the bottom of the lagoon. Local authorities have blamed natural phenomena but state authorities and environmental investigators have rejected this, blaming "poor management".
Attention has now turned to the wastewater treatment plants that operate nearby, and mud from the plants could be to blame.
Difficult words: spark (to start something), wastewater treatment plant (structure which cleans water), co-operative (organisation), authority (somebody in charge of something or somewhere),phenomenon (something which happens in nature).