Federal regulators are considering retesting water supplies at a small town in Pennsylvania that residents say have been contaminated by natural gas drilling.

Just a month after declaring water in Dimock safe, officials from the Environmental Protection Agency are taking another look after new evidence provided by residents suggested that drinking water could be more polluted than originally thought.

“We believe that additional information is needed to better understand the situation in Dimock and respond appropriately,” an EPA spokeswoman told Reuters on Thursday, after receiving hundreds of pages of data from Dimock residents.

“EPA is considering next steps including conducting some samples of well water in the area,” the spokeswoman said.