SOUTH BERWICK – Residents in South Berwick have been told that arsenic levels in their drinking water exceeded federal standards in recent months.

The Portsmouth Herald reports the notice says water tests covering April through September show the average level of arsenic, over four quarterly samples, was at 11.95 parts per billion (ppb), above the maximum contaminant level of 10.

The results are from a station that accounts for about 21 percent of the water produced by the district. John Leach, superintendent for the South Berwick Water Department, says the levels have already fallen back below the federal limit.

The water district serves about half the town of about 7,200 residents.

Leach said while the drought may have caused the elevated levels, it’s not known for sure.