A rare white tiger has been killed by two lions in a zoo in northern Czech Republic, a zoo official said Thursday.

The lions, 14-year-old Sultan and 11-year-old Elsa, managed unexpectedly to enter an open-air area occupied by the 17-year-old tiger Isabella, by opening a trap door leading to it, Liberec Zoo spokesman Ivan Langr said.

It happened quickly before the door to their area could be opened, Langr said.

He said authorities were not able to prevent the killing, which took place Thursday morning.

The two lions have been in the zoo since 2001.

The lions and tigers in the zoo share the same pavilion overnight, which they leave for separate open-air areas during the day. The animals are allowed to enter various areas on a rotating daily basis and the lions likely were trying to enter the place where they spent the previous day, Langr said. He said the zoo will abandon the rotating system following the killing.

The pavilion was built in 1994 and the system has been in place since. No such accident has happened before.

The Liberec Zoo is the only one in the Czech Republic that has white tigers.

Isabella arrived as a 2-year-old in 1994 after it was bought together with her brother, Columbus, from the Eskilstuna Zoo in Sweden. There are three more white tigers at the zoo — Paris, Surya Bara and Artemis, the daughter of Isabella.

White tigers are the result of both parents having a recessive gene for white coloration. They are rare in the wild because standing out in the jungle hinders their efforts to catch prey.

The zoo, established in 1919, is the oldest in the Czech Republic. It has about 1,000 animals.