(CNN) -- Muddy but unhurt, three University of Texas students emerged from a cramped cave complex in Austin, Texas, after a day-long search Sunday.

A rescuer at the entrance to Airman's Cave in Austin, Texas, Sunday.

Lt. Matt Cox, an Austin Fire Department spokesman, said the students -- two women and one man -- were reported missing early Sunday after a trip into Airman's Cave, about four miles south of the university's campus.

They were found about halfway down the 12,000-foot-long cave, which has few spaces big enough for an adult to stand upright and is explored primarily by experienced spelunkers.

The students were located shortly before 5 p.m. (6 p.m. ET), about 30 hours after they entered.

Their names were not released Sunday night.

A friend called 911 to report them missing at 5 a.m. The group had told friends to call 911 if they were not back by midnight Sunday, according to Austin-Travis County Emergency Medical Services.

Earlier reports that four students were in the cave were incorrect, Cox said.

Authorities did not know Sunday evening why the students were in the cave for so long.

But Cox said it would have been easy even for experienced cavers to get lost in Airman's, which he compared to the roots of a tree.

"There are so many ways to go," he said. E-mail to a friend
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