Two female giraffes at a zoo in central Poland died after vandals broke into the facility, and officials are trying to find a companion for their last remaining giraffe _ a male.

The break-in at the zoo in Lodz city occurred Saturday night, and the unidentified hooligans overturned signs and threw benches and garbage cans into animal runs, including one near where the three giraffes were.

One of the female giraffes _ 3-year-old Suri _ was found dead early Sunday, and tests indicated it died of stress and a heart attack, zoo Director Ryszard Topola said Tuesday.

The other female giraffe, 6-year-old Hana, was found dead early Monday, and Topola said the sudden stress worsened its ongoing treatment for parasites.

"These are wild animals and very skittish," said Topola, so there is little doubt that the fear contributed to their deaths.

The two females and the surviving 6-year-old male _ Tofik _ are from the endangered Rothschild giraffe subspecies, and the zoo's goal had been for them to be companions for years and hopefully mate and produce other giraffes.

"This is a very sad occurrence to us, a great loss," Topola said.

The head of the zoo's breeding section, Wlodzimierz Stanislawski, said management is checking with other European zoos to see they can provide a companion for Tofik.

"It is a tough task because there are not many available female Rothschild giraffes in zoos, but we will try to fill in this sudden gap," Stanislawski said.

Meanwhile, city authorities and the national Animal Guard watchdog organization have offered a 5,000 zlotys ($1,500; euro 1,100) reward for any clues that help find the hooligans.

Investigators also are trying to find out why the zoo's security guards didn't call police until hours after the hooligans had left the facility, which is not equipped with CCTV cameras.