Updated

JOPLIN, Mo. -- More than 230 people remain unaccounted for four days after the deadliest single tornado in more than six decades tore through the middle of Joplin, Missouri officials said Thursday.

Andrea Spillars, deputy director and general counsel for the Missouri Department of Public Safety, said a list of the 232 names will be released later Thursday. She urged survivors to check in.

Officials said previously they believe people who are unaccounted for aren't necessarily dead or trapped in debris. They say many are probably safe and but failed to tell friends and family where they are. Cell phone service in Joplin remains spotty.

"Our goal is to get that number to zero," Spillars said of the missing. "We will dedicate as much state resources as needed around the clock to ensure those family who have loved ones that they cannot find are connected."

The death toll rose Wednesday to 126 people, and officials have estimated more than 900 were injured.

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Spillars said officials know some of the people on the missing list are dead, but she wouldn't say how many. Some of the 126 bodies already found have not been identified.

Search-and-rescue teams have made multiple sweeps through the destruction, using dozens of dogs and listening devices in hopes of picking up the faint sound of anyone still alive beneath the collapsed homes and businesses. No new survivors have been pulled from the rubble since Tuesday.

Among those still missing is 16-year-old Lantz Hare. He was driving with a friend who said the two tried to take cover in the parking lot of a grocery store. The tornado shattered the windows and crumpled the car, and Lantz's father, Mike Hare, found his son's backpack in the wreckage.

Mike Hare has called hospitals from Dallas to Kansas City and taken dozens of calls offering advice, prayers and hopeful tips. None of the calls came from Lantz or offered any hope he might still be alive. But Hare said he'll keep searching until he finds his son.

"We know he's hurt somewhere," Hare said Wednesday, his voice breaking. "We just can't sit and keep calling. You've got to be moving."