MONTECITO, CALIF.—Hundreds of rescue workers slogged through knee-deep ooze and used long poles to probe for bodies Thursday as the search dragged on for victims of the mudslides that slammed this wealthy coastal town. Seventeen people were confirmed dead and 16 were missing. Family members anxiously awaited word on loved ones who hadn’t been heard from since the onslaught early Tuesday. “It’s just waiting and not knowing, and the more I haven’t heard from them — we have to find them,” said Kelly Weimer, whose elderly parents’ home was wrecked. The couple, Jim and Alice Mitchell, did not heed a voluntary evacuation warning and stayed home to celebrate Jim Mitchell’s 89th birthday. As search dogs clambered on heaps of wood that used to be homes, mud-spattered rescue teams from all over California worked their way through the ruins of Montecito, an enclave of 9,000 people northwest of Los Angeles that is home to celebrities such as Oprah Winfrey. It was left covered with thick muck, boulders, wrecked cars, splintered lumber and tree limbs in a scene Santa Barbara County Sheriff Bill Brown likened to a First World War battlefield.