Thousands of fishes were found dead in a river at an old palace in Beijing, known to locals as Yuanmingyuan Park, over the weekend, warning the city of its environment worries ahead of next year's Olympic Games, Xinhua reported. Nearly 10,000 dead fish were seen floating in a 200-meter long river that flows into the "Sea of Happiness". The river has become stinky since Saturday with dead crucian carps. The bigger ones are as big as an adult's palm and the smallest ones are about the size of the thumb. No dead fish has been spotted yet in the main lake. A forestry worker at the park said they had sprayed pesticide on trees on the river bank last week. "Probably we used too much pesticide and poisoned the fish," he said on condition of anonymity. Yet dead fishes are also found along dozens of meters in another river in the northern areas of the park, though no plants are seen anywhere near the river. A worker at Yuanmingyuan's management office said they were seeing into the matter and would expect "relevant departments" to help investigate.