The arrest today of an 18-year-old high school senior brought to 16 the number of Howard County residents arrested after an undercover investigation of drug use in county high schools, police said.

Scott Mason Jenkins, a Hammond High School senior, was arrested in Prince George's County and charged with selling LSD-soaked blotter paper, said Sgt. Paul Hajek, a Howard police spokesman.

Jenkins, later freed on his own recognizance, was one of several Howard County high school students who were arrested after allegedly selling small quantities of drugs to a 19-year-old police cadet posing as a Hammond High School junior.

Jenkins, accompanied by his parents, surrendered early today to Prince George's police in Bowie, where he was later identified by Cadet Tim P. Black. Jenkins was arrested in Prince George's because the alleged drug sale took place in that county, police said.

Earlier this month, 11 students and one adult were arrested for selling drugs to Black, who was the third Howard County officer in five years to pose as student in a drug investigation.

In addition, Howard police last Friday arrested three others on charges stemming from Black's investigation, Hajek said.

Police arrested John S. Piper, 18; John T. Layne, 25; and John F. Donellan, 19, all of North Laurel, on a variety of drug charges, including possession of marijuana, police said.