The clock tower looms high above the Georgetown University campus on May 1. Police believe the clock hands of the Gothic-style flagship building, a National Historic Landmark, were removed this past weekend. (Mark Gail/THE WASHINGTON POST)

As Georgetown University tour guides lead visitors past Healy Hall, they often point to its iconic clock tower and explain that generations of mischievous students have attempted to steal the clock hands and mail them to the pope. But that hadn’t happened in more than six years.

This week, a hands-free clock face proved that the pranksters are back.

“I don’t understand how that is even possible,” senior Amanda Reese said Tuesday afternoon as she shaded her eyes and gazed up at least six stories to the clock face and a small square door that someone might pop open to nab the hands.

The hands disappeared sometime before dawn Monday, the last day of class. Late that afternoon, maintenance workers removed the hands from a second clock on the back side of the tower to check for damage.

Campus police are searching for a 51-inch minute hand and a 38-inch hour hand. A university spokeswoman called the theft “a serious violation of Georgetown’s Student Code of Conduct.”

There is little documentation of the history of this tradition, although generations of students have written their initials or nicknames, along with the date, inside the clock tower, according to those who have been there. The prank dates to at least the 1960s, although the tradition of mailing the hands from the Jesuit university to the Vatican apparently didn’t start until the 1970s.

The prank is much more difficult to execute these days, because the tower’s staircases and passageways are barricaded. After the last theft in September 2005, the university added more security.

“There are not a lot of ways that you can stop them,” said Thomas D. Erb, president of Electric Time Co., based in Medfield, Mass., one of the world’s largest suppliers of tower clock hands. (The company did not supply the Healy hands, and a Georgetown spokeswoman was unable to identify the provider.) Erb said he has responded to dozens of such pranks during his 25-year career. “They are very creative.”

Pranks are rife at colleges as seniors seek to make a mark before they graduate and other students try to escape the stress of finals. But college administrators worry that these adventures can lead to injuries, lawsuits or expensive damage.

The 2005 Healy hand heist was executed by a junior and a freshman who shared a love of ad­ven­ture and climbing. They seized the hands early one September morning but were caught later while trying to return the goods. They were nearly suspended, but instead they had to complete dozens of community service hours and write essays about Georgetown traditions that are less dangerous.

“We were just looking for an ad­ven­ture, that’s all,” said Wyatt Gjullin, now 24, who is graduated in 2009 and is living in Seattle — working, studying for his LSATs and waiting on a Fulbright application.

The two men said they learned the hard way that Georgetown officials do not approve of students risking their lives and committing crimes in the name of tradition.

“We didn’t really anticipate the university being that upset about it,” said Drew Hamblen, 27, who is in the Navy and based in Norfolk.

That morning, the two scaled construction scaffolding near Healy, the university’s main administrative building. They climbed through an open window and trekked up the staircases inside.

“There are a number of locked doors,” Hamblen said. “There are ways to get around locked doors. Or unlock them.”

The two eventually reached a room with a trapdoor in the ceiling, which led them to the heart of the bell tower. They opened a small square window in the clock face and peered out.

“It was pretty serene and surreal,” Gjullin said. “You could see so much.”

The two students tried to strip the hands from the clock that faces Georgetown’s main gates but couldn’t. So they tried the second clock, on the back of the tower. After more than an hour, the hands were theirs. They walked downstairs and out the hall’s front door.

The pair told a few friends what they had done, and Hamblen showed the hands to his Bible study group. Meanwhile, the university announced an intense investigation. The culprits wondered: Would their friends rat them out? Would Gjullin’s initials inscribed in the tower give them away? And why did some anonymous person write to the student newspaper and claim credit?

A few weeks after taking the hands, the two students decided to return them. But they wondered how. Hamblen’s roommate volunteered to take the hands directly to campus officials. That led to questions, confessions and a slew of disciplinary charges.

Hamblen and Gjullin were put on academic probation but stayed out of trouble for the duration of their time on campus. They graduated and moved away.

Meanwhile, the university spent $25,000 to buy additional hands, fix some damage to the clock and install even more security.

This week, Gjullin and Hamblen found themselves tagged in Facebook posts about the disappearance of the Healy hands. News spread through Twitter, too. The university, capitalizing on the publicity moment, even posted a photo of the handless clock on its social media accounts with a caption that described the image as “a visual reminder that Georgetown is timeless.”

“I was pretty pleased to hear the news,” Gjullin said.

Hamblen was also excited to see the tradition continue, although he hopes the hands will be returned undamaged. And he hopes that if the pranksters are caught the university doesn’t throw the book at them.

“They should be cool about this,” he said, “and embrace the tradition.”