CHARLESTON, W.Va. -- A team of researchers suggested to legislators Monday that West Virginia start monitoring coal slurry even though their just-released study found no hazards to public health.

The West Virginia University scientists cited the "huge" data gap that hindered their efforts, and called it "logical" that the wastewater played a role in some of the increases in toxins they found.

"We can't assure safety. We didn't find a health hazard," said Dr. Alan Ducatman, the study's lead investigator and a physician.

Ducatman and fellow researcher Paul Ziemkiewicz said the results left them unable to say whether the state should end or extend its ban on new sites for pumping slurry underground. Coal operators inject this liquid left over from washing coal into exhausted mines as a cheap way to store it.

The researchers also said that filling the data gap would require a large-scale, long-lasting and costly study that would likely require federal funding and substantial advance planning.

While the industry defends this storage method as safe, critics argue that both blasting and natural shifting beneath the earth can allow this slurry to leak into drinking water supplies. Residents of such communities as Prenter and Rawl have sued coal companies, alleging slurry has poisoned their wells and made them sick.

The Department of Environmental Protection provided the study's testing data and has said it excluded Prenter and Rawl because of the pending lawsuits. Several members of the House-Senate panel that received the study results Monday questioned that decision.

"My concern is, we didn't check those places," Delegate Tim Manchin, D-Fairmont, said at one point.

Delegate Don Perdue said the Department of Health and Human Resources, which assigned the study to the WVU researchers, should have pushed to include those sites.

"You should have been driving that issue, because it is one of public health," said Perdue, D-Wayne, who chairs the House's health committee. "Where a health issue of this magnitude is involved, you should be on an equal playing field with DEP."

But Delegate Mike Ross, D-Randolph, cited the absence of findings linking slurry to health hazards. He noted the industry's role in the economy of West Virginia, the country's second-largest coal producer.

Analyzing tests results from four injection sites, the researchers found no unsafe levels of some of the worst toxins found in slurry such as arsenic, lead and selenium. They did find raised levels of such lesser toxins as aluminum, iron and manganese, but could not identify slurry as the culprit.

"We did not document a health hazard that is specifically related to coal slurry injection," Ducatman said. "This does not imply that the safety of this practice is assured."

He and Ziemkiewicz recommended a monitoring program that checked for a wide range of hazardous substances and involved frequent sampling -- including before slurry is pumped into a new underground storage site.

DEP began requiring operators at the dozen or so existing injection sites to monitor for potential pollution problems last year, after its review of testing data proved inconclusive. It also announced a temporary moratorium on new site.