PITTSBURGH — Members of the leading Marcellus Shale industry group in Pennsylvania will voluntarily disclose chemicals used in each natural gas well as of Jan. 1, the organization said.

An environmental group applauded the move, but said it’s not enough.

The Marcellus Shale Coalition represents many of the largest gas drillers in Pennsylvania.

The drillers use a process called fracking, which forces millions of gallons of water, mixed with sand and chemicals, deep into shale formations to free the gas.

The industry believes the process is safe, but environmental groups and people who live in drilling areas have worried about the exact chemicals used in each well, and the possibility of groundwater contamination.

Kathryn Klaber, president of the Marcellus coalition, said that the full disclosure was an “obvious choice” that the group’s members had no problem supporting.

The disclosure will be mandatory for members, who will list the chemicals used in each well on the website FracFocus.org.

The state of Pennsylvania already requires drillers to list all chemicals used in drilling on a website.

But that doesn’t tell people what’s being used in a specific well near them.

Klaber said the group wanted to go beyond what the state requires.