The mystery behind the disappearance of an Italian teen 36 years ago intensified Thursday as the tombs of two 19th-century princesses buried at the Vatican were unsealed.

Not only was the body of Emanuela Orlandi not found, but neither were the remains of Princess Carlotta Federica or Princess Sophie von Hohenlohe.

“The last thing I expected was to find empty tombs,” said Orlandi’s brother, Pietro Orlandi, 60.

Emanuela, the daughter of a Holy See employee whose family lived within the Vatican walls, was last seen leaving a music class at age 15 in 1983.

The graves at the Teutonic Cemetery were opened based on an anonymous tip the family received last summer, according to CBS News.

“I received a letter with a picture in it,” Orlandi family lawyer Laura Sgro told the network. “The letter said: ‘If you want to find Emanuela, search where the angel is looking.'”

The note was referring to a marble statue of an angel holding a book that reads “Requiescat in Pace,” Latin for “Rest in Peace,” and peering down at the tombs of the German princesses at the cemetery.

When the family went to visit the site, they noticed that one of the tombs had recently been opened.

“There was new cement on it, but we didn’t know why or when, we were given no information,” Sgro said.

The family sent a request to the Vatican secretary of state to have the tombs opened, which was granted last week.

Both graves were opened because of their proximity to one another and to “avoid possible misunderstandings about which grave is the indicated grave,” a Vatican tribunal said.

Forensic scientists conducted the dig on Thursday, outfitted in white suits, masks and head lamps to search the underground chamber.

But after just a couple hours of work, the Vatican released a statement with the shocking findings — or lack thereof.

“The result of the search was negative. No human remains or funeral urns were found,” Vatican spokesman Alessandro Gisotti said.

The Vatican said the families of Federica, who died in 1840, and von Hohenlohe, who died in 1836, have been notified that their remains are missing.

It also said it would look into work done on the tombs in the 19th century, and again in the 1960s and ‘70s.

For decades, wild theories have swirled in the Italian media about Orlandi’s disappearance. Some have said she was kidnapped by the Mafia to put pressure on the Vatican to cough up a loan.

Others say she was taken in a bid to get Mehmet Ali Agca released from prison. He is the Turk who attempted to assassinate Pope John Paul II in 1981.

In 2012, the tomb of notorious mobster Enrico De Pedis was exhumed at a Vatican church — but the bones found inside could not be matched to Orlandi.

And last year, a bag of bones was found during ground work at the Vatican embassy in Rome, but DNA tests turned out negative.

With Post wires