The state Department of Health is investigating a mysterious spill that left more than 6,000 gallons of pinkish, reddish, purplish muck in a channel near Kawaikui Beach Park in Aina Haina.

The department Friday was testing water and sediment samples in an effort to determine what fouled a significant stretch of the concrete waterway that runs to the ocean makai of Kalanianaole Highway.

No pollution apparently reached the ocean.

Janice Okubo, department spokeswoman, said staff members Wednesday responded to a call from environmental activist Carroll Cox notifying them of the problem. Following an investigation, the department’s cleanup contractor was called out to take care of the mess.

Samples were taken for lab analysis, and the initial analytical screening ruled out petroleum, semivolatile organic compounds and pesticides, Okubo said. Microscopic observation revealed no algal growth.

Further testing is underway to detect the presence of heavy metals to determine elemental makeup. Sediment samples were also taken, she said.

Cox, who heads the nonprofit EnviroWatch, said a fisherman called him about the spill Monday, and when he finally was able to check it out a couple of days later, he was alarmed.

“I was concerned that with the rain we’ve been having that it would wash out to the ocean and be introduced to Maunalua Bay,” he said. “It could have easily made its way to the ocean. Who knows what kind of serious negative impacts there could have been in the bay.”

A sand berm in the channel appeared to block the unknown substance from reaching the ocean.

“Thank God for poor maintenance,” he said, laughing and adding that he normally advocates clearing channels to prevent flooding hazards.

Cox, who returned to the scene Friday, praised health officials for acting quickly to take care of the problem during the holiday week.

“This is one of those times where I’ve got to say ‘Wow,’” he said. “They really struck up the band and were in time, in step, and they didn’t marginalize this.”

But the effort might have been too late for some feathered victims. Cox said that after seeing a couple of agitated adult ducks along the channel separating large residential oceanfront properties, he discovered two dead baby ducks.

While it wasn’t exactly clear how the ducklings died, a state Department of Land and Natural Resources biologist took them for evidence, he said.

Cox urged anyone who witnesses or discovers a chemical spill to call authorities immediately.

“We’ve got to care a lot more than we do,” he said. “The ocean is not a dump site.”