Hundreds of dead fish surfaced in a stream in Istanbul's Zeytinburnu district after maintenance work by the Istanbul Water and Sewerage Administration (ISKI) cut off the water flow for several days, leaving behind a foul odor and prompting an official investigation.

The fish were found floating in the Çırpıcı Stream, which flows into the Sea of Marmara from the Kazlıçeşme neighborhood. Municipal teams removed the dead fish trapped behind a barrier after the stream's connection to the sea was temporarily blocked during ongoing infrastructure works.

The reduced water level, caused by the maintenance operations, has also led to a strong smell in the surrounding area, while seagulls were seen feeding on the remaining fish.

ISKI crews continue wastewater, stormwater, cleaning, and repair works at the site.

The incident has drawn complaints from residents and visitors spending the weekend at the nearby Aytekin Kotil Park.

"We won't come here anymore," said Tayfun Kızılkaya, who was picnicking with his family. "All the fish are floating dead on the water. Whoever is responsible should resolve this as soon as possible. This is a public park where people come to relax."

Local shopkeeper Oğuzhan Kuyumcu blamed the fish deaths on the interruption of the stream's water flow rather than pollution.

"They blocked the stream, so no fresh water is entering," said Kuyumcu, who has fished in the area for 25 years. "The stream has effectively turned into a pond, and the fish were left without oxygen. This wasn't caused by chemicals or poisoning. The fish died because they were trapped in oxygen-deprived water."

Authorities launched an investigation after reports of large numbers of dead fish washing ashore.

Teams from the Disaster and Emergency Management Authority (AFAD), the Turkish Coast Guard, and the municipality secured the area, while AFAD collected water samples for laboratory analysis to determine the cause of the fish deaths.

According to reports, ISKI has been carrying out maintenance work in the stream, which is connected to the Sea of Marmara, for about four days. During the operation, the water level dropped significantly, and dead fish began appearing along the shoreline on Sunday evening.

Officials have not yet announced the results of the water analysis or confirmed the exact cause of the incident.