OCEANSIDE -- City detectives culminated a six-month undercover investigation into the street sale of illegal drugs Thursday with a two-county sweep that netted one suspect.

Oceanside police were seeking seven adults and two juveniles Thursday who they say sold undercover detectives small amounts of marijuana, methamphetamine and Ecstasy, said Lt. Joe Young.

Detectives arrested one man, 28-year-old Peter Murley, in the 800 block of Summer Song Court in Encinitas on suspicion of the felony sale of marijuana, Young said. The sweep continued Thursday evening, and Young said he expected more arrests.

The investigation began in June after citizens reported seeing "suspicious hand-to-hand exchanges" near the Regal Theater on Mission Road and along Coast Highway. Young said residents continued to call police detectives with observations that helped move the investigation forward.

Beginning in June, eight plainclothes detectives with the city's Special Enforcement Detail conducted a series of "drug buys" over several months, Young said. Wired for sound and watched by other detectives, undercover detectives bought drugs from suspects, he said.

Young would not say if informants played a role in the investigation.

Young said that he did not know how much money detectives used to buy the drugs or what quantities of drugs were bought and that officials were still tallying those details. Young said all of the purchases were for small quantities of drugs.

Based on their observations, detectives obtained arrest warrants for eight suspects and sought those suspects at six addresses in Oceanside on Thursday afternoon, Young said. Detective sought the ninth suspect on probable cause.

Police found no suspects at home Thursday so they began looking for them on the streets, he added.

Teams also served arrest warrants in Encinitas and in San Bernardino County, Young said.

Other than hanging out in Oceanside, no common personal characteristic connected the suspects, Young said.

"These are people who spend a lot of time in the downtown area at all hours, day and night," he said.

The investigation turned up no evidence of violence, weapons, gang involvement or organized drug sales among the suspects, Young said.

Thursday's drug sweep was small in comparison to investigations into drug trafficking in the late 1990s, Young said.

"Downtown Oceanside is nothing to what it used to be," he said, crediting the downtown redevelopment plan and increased police enforcement with reducing drug sales and drug-related crime.

Contact Philip K. Ireland at (760) 901-4043 or online at pireland@nctimes.com.