DENVER (AP) -- Colorado oil and natural gas regulators have approved a rule making the state the first to require energy companies to do groundwater sampling both before and after they drill.

The sampling of water wells near drilling sites will help show whether supplies of drinking water have been affected by energy development.

The Colorado Oil and Gas Conservation Commission approved the rule Monday as it began a three-day hearing on rule changes. Next, the commission will consider updating how far drilling must be from buildings.

Some environmental groups and Boulder County had expressed concern that the rule allowed for less sampling in the energy-rich Wattenberg Field in northeast Colorado, including Weld County. The commission says an existing program in Weld County provides water well testing to any well owner requesting it.