OAKLEY -- A raid of a large marijuana grow in Oakley on Friday evening yielded several thousand plants, but no suspects, police said.

At about 5:30 p.m., the Contra Costa Sheriff's Office helicopter was patrolling the Delta when officers spotted a pot farm on the outskirts of Oakley, spokesman Jimmy Lee said in an e-mail. Oakley police officers and sheriff's deputies from the Delta Station discovered several thousand marijuana plants and evidence of a camp at the site. Officers initially believed a suspect was at the scene, but they didn't find anyone, Lee said.

Oakley police Sgt. Jeff Solomon said the pot farm was off Sellers Avenue and near the Contra Costa Canal. He described the landscape as marshy, with many large bushes.

"It's hidden pretty well," Solomon said.

The investigation is ongoing.

Lisa P. White covers Martinez and Pleasant Hill. Contact her at 925-943-8011. Follow her at Twitter.com/lisa_p_white.