ALTUS, Okla. (AP) _ An Oklahoma Highway Patrol trooper went undercover at Altus High School and helped in a narcotics investigation that resulted in the arrest of three students and an adult.

District Attorney John Wampler says 21-year-old Florencio Martinez and the three students were arrested Thursday on complaints of distribution of a controlled dangerous substance within 2,000 feet of a school or park.

Wampler says the investigation was initiated at the request of school officials who were concerned about drug problems at the school.

The OHP trooper posed as a senior at the school to determine the seriousness of the problem and buy drugs.