The U.S. Immigration and Customs Enforcement sweep happened on Monday morning, advocates said. Credit: AP/Erin Hooley At least three people were arrested by federal immigration agents in Riverhead on Monday morning, according to eyewitnesses and volunteers with the nonprofit OLA of Eastern Long Island's rapid response network, who said the agents carried out a series of enforcement actions through residential and commercial areas. The activity further rattled a community that's already on...