HOUSTON (AP) — The amount of explosive gas tainting a North Texas neighborhood’s water supply has increased in recent years, but the state’s oil and gas regulator says it can’t link the methane to drilling activity nearby, according to a report it released Wednesday.

The state Railroad Commission has found that the contamination has gotten worse in most of the private water wells it tested in September 2013 compared with what was measured in 2010 and in 2011. However, Peter Pope, the agency geologist who signed off on the report, wrote that staff “has determined that the evidence is insufficient to conclude that Barnett Shale production activities have caused or contributed to methane contamination beneath the neighborhood.”