PORTLAND — Authorities say more education about drug-impaired driving is needed in Maine as the state deals with a heroin epidemic and considers legalizing marijuana for recreational use.

The Portland Press Herald reports prosecutors, police officers and traffic safety experts made the comments during a summit in Portland on Monday that examined new research and approaches to dealing with drivers under the influence. The summit was hosted by AAA Northern New England and the Maine Bureau of Highway Safety.

Alcohol remains the primary intoxicant for people driving but officials say more people are using drugs while driving. Col. Robert Williams, chief of the state police, says authorities “have no idea how big the problem is.”

Officials say the state’s also facing a problem dealing with drivers using legally obtained prescription drugs.