RICHMOND -- Three Richmond residents suspected of selling methamphetamine in Marin County were arrested Friday after a bust in San Rafael.

Ascencion Medina, 35, Martin Sarmiento Morales, 44, and Kristin Salazar Muro, 20, were booked into Marin County Jail on suspicion of narcotics sales and conspiracy. Investigators are seeking additional suspects.

Investigators identified Medina as a source of the meth and set up a series of undercover drug buys, said sheriff's Sgt. Pierre Ahuncain.

On Friday, an undercover detective paid Medina $6,000 for a half pound of suspected meth, then arrested him on Andersen Drive in San Rafael, Ahuncain said.

Investigators then executed three search warrants in Richmond and arrested Morales and Muro, who allegedly participated in the drug sales. San Rafael police, Novato police and the California Highway Patrol assisted in the operation.

Detectives seized more than two pounds of suspected meth over the course of the investigation.