Lincoln, Neb. — A passenger’s cell phone automatically alerted emergency services after a car crashed into a tree early Sunday morning in Nebraska, killing all six young passengers, authorities said.

Five men in a Honda Accord died at the scene of the crash about 2:15 a.m. in Lincoln, about 3 miles east of the state Capitol, police said. The 24-year-old woman died later at the hospital, where she was taken in critical condition.

The 22-year-old driver is among the five dead. The other victims are one 21-year-old, one 23-year-old and two 22-year-olds.

Police said the cause of the crash was under investigation, and they said the crash was reported by an iPhone that detected the impact and automatically called 911 when the phone’s owner didn’t respond.

“This is the worst crash in Lincoln in a long time,” said Lincoln Assistant Police Chief Michon Morrow. “We tried to come up with another disaster like this, but we didn’t come up with anything.”

Investigators were unable to locate any witnesses to the crash as of Sunday afternoon, which could make it difficult to determine what happened.

“We will need some time to determine the cause of this accident,” Morrow said. “We are looking at all possibilities, including alcohol, speed or distracted driving.”