CONTRA COSTA COUNTY -- Four people were arrested after agents from the FBI and Drug Enforcement Administration raided homes in four cities Tuesday morning, an FBI spokesman said.

Few details about the arrests were released, but spokesman Peter Lee said that the agencies, which received help from the Contra Costa County Sheriff's Office and Antioch police, raided homes and served arrest warrants in Pittsburg, Antioch, Oakley and Concord. He did not say how many homes were targeted.

A SWAT team was used in the raids, he said and the drugs seized were methamphetamine and cocaine. The FBI did not specify the quantity of the drugs taken.

"We could not have done this without the tireless work of so many people over a long period of time," Lee said. "It took a huge effort from everyone."

Authorities arrested Jorge Herrera, 47, of Pittsburg but Lee declined to release the names of the other three people arrested because the investigation is ongoing.

All surrendered peacefully, Lee said.

Contact Rick Hurd at 925-945-4789 and follow him at Twitter.com/3rdERH.