Maribel Mori asked her teenage son to fetch water yesterday morning.

Michael John came back with a pail of fish locally known as "potpot."

He and other residents had collected the fish, which were floating dead along the coastal waters of barangay Ibo, in Lapu-Lapu City.

A few hours after eating the fish, which was cooked with vinegar as inun-onan for breakfast, Maribel was at the barangay health center complaining of nausea, vomiting and headache.

She told health workers she started to feel sick after eating the fish.

"Murag nang hugot akong panit unya ni init akong nawng (It felt like my skin tightened and my face burned)," said Mori.

Health and fishery officials yesterday started looking into the origin and cause of the fishkill in barangay Ibo, where thousands of fish have turned up dead.

Pollution is the most common cause of a fishkill.

But Dr. Rodulfo Berame, chief of the City health Department, said it could also be a result of the seasonal low tide in December.

He warned Ibo residents not to eat the dead fish or sell it pending results of a laboratory examination.

Samples of the seawater and fish were gathered by city health personnel yesterday. Results will be known after three to four days.

Health workers will check the quality of the seawater for chemical oxygen demand (COD) and its biological oxygen demand (BOD).

Dr. Berame said that if the fishes were killed by pollution or chemicals, many other residents would have gotten sick.

Some residents told radio dyAB pointed to the wastewater from two companies at the Mactan Export Processing Zone as a possible source of pollution.

Company representatives were supposed to hold a dialogue with barangay residents yesterday but asked barangay captain Cahilog to postpone it to next week because their Christmas parties were scheduled yesterday afternoon.

Resident Cynthia Honda said she thought the fish was an early Christmas presence.

"Panagsa ra kaayo ni ang grasia ihatag sa amo kay kada December ra jud ni siya mahitabo. Sympre grasia nani mao amoa lang gipahimuslan (It is rare that such blessing will come to us because this only happens every December. Of course, we will take advantage of this blessing)," she told Cebu Daily News.

She joined her neighbor in collecting the floating fish about 5 a.m. yesterday.

She wasn't bothered by the warning that eating the fish was a health risk.

Honda, a mother of three children, said she would leave their fate to God.

Honda said she cooked the fish as inun-onan but didn't get sick after eating it. She had two kilos of fishes also processed into dried fish.

Lapu-Lapu City Administrator Teodulo Ybañez ordered the City Health Department to investigate the matter.

"What happened was part of the cycle if there was a low tide. Ang mga isda kay buhi paman gani pag kuha sa ubang residenti (Some of the fishes were still alive when these were gathered by the residents)," said Dr. Berame, health department chief.

He said islets in Lapu-Lapu also had reports of fishkills during low tide.

During low tide, he explained, there is low supply of oxygen in the water, causing the fishes to weaken or die.

"We are asking residents not to eat the fish because we don't know yet what killed them," said barangay captain Ferdinand Cahilog

He said he ordered the confiscation of dead fish gathered by residents .

Cahilog said he suspects water pollution or contamination was a cause.

Allan Poquita, assistant regional director of the Bureau of Fisheries and Aquatic Resources (BFAR), sent personnel to investigate what caused the fish kill.

"We just learned about the fish kill so we cannot yet determine what caused it," he said.

Until the cause is known, Poquita asked Ibo residents to refrain from collecting and eating the dead fish.