The state Department of Health is trying unravel the mystery of who's behind a large illegal landfill in a remote region in Wai'anae. For years, the site has been the end point of hundreds of tons of buried hazardous waste materials, officials suspect.

On Thursday, the state got an assist from a group of educators, students and residents who inspected the dump site on their own and uncovered documents that could lead to those who've been getting rid of commercial waste on the sly.

One member of the group phoned in a complaint from the scene. But it wasn't the first time state officials had heard complaints about the landfill.

Steven Chang, chief of the Solid and Hazardous Waste Branch for the DOH, said the materials appear to be construction demolition debris dumped illegally on Department of Hawaiian Home Lands property.

He said his branch had previously sent letters to DHHL alerting them to the situation.

"We are going to be meeting with Hawaiian Home Lands people next week at the site, probably, to take a look at what's going on," Chang said. "Apparently, this has been going on a long time."

Chang said investigators would be trying to determine who's responsible. He said the massive amount of waste dwarfs the state's definition for illegal dumping — which is anything more than one cubic yard.

The previously secret landfill is on the north side of of Highway 782 about a quarter of a mile east of where it intersects Wai'anae Valley Road. Access to the dirt road leading to the dump site is blocked by a pipe fence latched with a combination paddle lock and a "No Trespassing" sign.

Carroll Cox, an environmental activist and president of EnviroWatch Inc., was with the group that inspected and photographed the landfill on Thursday.

He described the site as a years-old "active landfill" about two acres in size and filled with "hundreds and hundreds of tons of hazardous solid waste and potentially toxic materials" dumped inside a gated and locked setting.

The materials include concrete blocks, old painted wood, asphalt, rebar, cast iron, hollow tile bricks, roofing materials and green matter. While much of the debris is covered with dirt, several recent mountains of rubble also decorate the canyon landscape.

"What's happened is that they buried the stuff and spread the dirt over it," Cox said.

"You can see where they've graded this. I mean, whoever's doing this is pretty bold. They are going in there with heavy equipment after they've dumped, and then bury it — smash it down and spread it out and put dirt on it."

Lucy Gay, director of Continuing Education & Training at Leeward Community College in Wai'anae, learned about the landfill from a colleague who hiked the isolated area over the July Fourth weekend and stumbled across huge debris piles.

Gay and area Hawaiian activist Alice Greenwood investigated the site on their own and contacted Cox. The three returned on Thursday, along with the students.

"We want to know who are the guys who are dumping all this stuff on the land," Gay said. "This is a big dump."

Gay, Greenwood and Cox uncovered documents among the materials that they think will help investigators locate the trash haulers.

"This is one of those difficult-to-find dumps that the Wai'anae Coast has been plagued with for years," Cox said. "Every canyon has played host to illegal dumping of this type. But this is one of the most clandestine examples I've ever seen."