MARIN COUNTY -- FBI agents raided a home in an exclusive San Rafael subdivision Thursday morning, but federal officials declined to say why they were in town.

In a spectacle that startled neighbors, a team of about 18 agents, joined by five San Rafael police officers, served a search warrant at 40 W. Seaview Ave., a 5,000-square-foot, four-bedroom, four-bath home on a ridge between the Dominican University neighborhood and the bay.

"At this time the affidavits are sealed and I can't go into further details," reported FBI spokeswoman Julianne Sohn. She declined to elaborate.

"We assisted the FBI," San Rafael police Sgt. Mike Vergara said. "I really don't have much comment on it."

One neighbor on the quiet street who asked to remain unidentified said agents wearing flak jackets pulled up in SUVs at about 7:15 a.m. and knocked on a door at 40 W. Seaview, telling a bystander they were serving a search warrant.

Some of the agents appeared to depart after about a half hour, but at least several others remained there several hours later.

FBI spokeswoman Sohn said she did not know when more information would be forthcoming, noting it is uncertain when the affidavits would be unsealed.

Contact Nels Johnson via email at ij.civiccenter@gmail.com. Follow him at twitter.com/nelsjohnsonnews