(CNN) -- Len Gengel cries between sentences. "It's my daughter's birthday today," he says, choking back tears.
"We should be celebrating," he says. "Instead, I'm talking to people all day long, making sure they continue on the search and rescue. That's my objective today: to keep that search and rescue going."
Gengel's daughter, Britney, is one of four students from South Florida's Lynn University who are missing amid the rubble of Haiti's Hotel Montana. Two faculty members from the university also remain missing.
Britney, a sophomore journalism major with jet black hair and a bright smile, turned 20 Thursday. She had traveled to Haiti with 12 Lynn University students on a humanitarian mission to feed the poor. Eight of the students were rescued last week.
An hour before the magnitude-7.0 quake, Britney called her mother. "Brit said she found her calling, that she knew what she wanted to do for the rest of her life," her father said, pausing to catch his breath.
"Who knew an hour later that was going to happen? It's so hard to talk about. ... Think of the worst day of your life and then times that by 1,000."
Crews have spent days searching mounds of rubble, 30 feet high in places, that was the Hotel Montana, popular with tourists and visiting officials.
Lynn University, which hired a search crew immediately after the quake, initially told the Gengel family that their daughter had been rescued. The family then flew from their Massachusetts home to South Florida for what they thought was going to be a reunion.
"We have spent a week here in Florida in a living hell," the father said. "It's just one of the dirtiest tricks life can play on you, to take someone from you and then call and say they found her and she's on a helicopter and she's gonna be OK. And then to be told 10 hours later ... that they had bad intel -- they don't have her."
Lynn President Kevin M. Ross said Thursday evening that he is still optimistic "that a miracle is found."
"We still have hope at Lynn University," he said. "The search and rescue will continue."
He also called upon the U.S. government to ensure that every person "lost in this tragedy are returned to their loved ones."
"We need a commitment to return the missing to the families," Ross said.
The university has been updating families regularly on the search efforts. Students have also rallied on campus, raising money for relief efforts in Haiti. T-shirts for sale have a simple message: "Lynn United."
Len Gengel said that his daughter was in Room 300 and that a CBS news crew showed him photographs of what was believed to be the room.
"She's in the back right-hand corner," Len Gengel said. "Her roommate was at the pool when this happened. My daughter was either showering or resting."
On a Facebook page dedicated to Britney, one message says, "Everyday miracles happen, I think today would be a perfect day to have one."
Her father says his family has been touched by the thousands of messages they have received: "The outpouring of support and love has just been amazing."
He says he's heartened that eight of the Lynn students were rescued. He continues to pray for others missing at Hotel Montana and across Haiti. But on this day, his thoughts are focused on the girl who brought him so much joy when she entered this world 20 years ago today.
"At this moment, we're trying to prepare ourselves for the worst, but we're hoping and praying for the best," he said. "We're devastated. Our hearts are broken. They're just broken."