(CNN) — Is it really safe?
West Virginia's governor is asking federal authorities to do further studies on the state's water after last month's chemical spill near Charleston.
"It is critical this study is funded and that work begins immediately," wrote Gov. Earl Ray Tomblin in a letter Tuesday to Dr. Tom Frieden, director of the Centers for Disease Control and Prevention.
The chemical -- 4-methylcyclohexane methanol, or MCHM -- leaked from a storage tank into the Elk River and from there into Charleston's water supply on January 9. Its licorice smell alerted residents to the contamination and led to a do-not-use order for 300,000 West Virginians, some of whom could not drink or bathe in their water for more than a week.
It also underscored that little is known about the chemical, which is used to wash coal prior to market in order to reduce ash.
The spill was originally estimated at about 7,500 gallons, but Freedom Industries said late last month that about 10,000 gallons of chemical had escaped. The company also told regulators that a second chemical -- a mix of polyglycol ethers, known as PPH -- was part of the leak.
"I am committed to the health and well-being of West Virginians and believe there is a pressing need to further study the potential health effects resulting from exposure to water contaminated with crude MCHM and PPH," Tomblin said.
An independent water test conducted early this month at CNN's request found trace levels of MCHM, both in untreated river water and in tap water from two homes in Charleston. The amounts ranged from less than 0.5 parts per billion to 1.6 parts per billion -- well below the 1 part per million that the CDC has said it considers safe.
"We stand willing to continue to assist and will be discussing with officials there what additional toxicology and epidemiology studies may be needed," said Laura Bellinger, a CDC spokeswoman.
Dr. Tanja Popovic, the director of the CDC's National Center for Environmental Health, told reporters on February 5 that repeated testing had shown the water to be safe.
"What I can say is that with all the scientific evidence that we have, with everything that numerous people have worked on so far, I can say that you can use your water however you like," Popovic said. "You can drink it, you can bathe in it, you can use it how you like."
Tomblin said then that tests had shown levels of less than 10 parts per billion or too low to detect, and that she and her staff had been drinking the water "for the last couple of weeks." But when asked whether she could declare it "100% safe," she said, "No."
"The only thing that we can rely upon is what the experts tell us, and, you know, for all the tests done that's who we've got to depend upon," Tomblin said.
A federal grand jury is probing the spill at Freedom Industries, sources familiar with the grand jury's activities have told CNN.