HANOVER, N.H. — Dartmouth College officials say a second private well near a Hanover farm where contaminated laboratory animals were buried in the 1960s and 1970s has tested positive for a toxic chemical believed to have migrated from the site.

Administrators said this week that the well is a residential water supply located nearly a mile northeast of Rennie Farm. Recent tests detected the chemical, 1,4-Dioxane, at concentrations below the state standard for water quality.

College officials say residents have been given bottled water.

The first private well contamination was reported about a year ago, after residents were informed the well contained 1,4-dioxane at twice the state water standard of 3 parts per billion.

The chemical is classified by the EPA as a probable human carcinogen.