A fossilized dinosaur egg, stolen Sunday evening from a display at the Japan Expo 2001 in Kitakyushu, has been found, exhibition officials said.

Police, who have opened an investigation, believe the thief secretly returned the egg sometime Tuesday after watching a television news item about the theft.

The stolen egg was one of four that expo organizers had loaned from Mongolia's national museum. A carnivorous dinosaur unearthed in the Gobi Desert had originally produced the eggs, which are believed to be 70 million to 100 million years old. Each egg measures 15 cm in diameter and weighs about 1.5 kg.

The eggs were displayed at the Mongolian pavilion's "Experience the Gobi Desert" section, where visitors could touch the exhibits, officials said.

The egg was discovered missing after the exhibition hall was closed Sunday evening. It is believed to have been stolen between 6:30 p.m. and the 8 p.m. closing time that day.

The stolen fossil was found around 8 p.m. Tuesday on sand about 1 meter from where the remaining fossil eggs were on show. It was damaged on the bottom, according to officials.

"We'd like to continue displaying the fossil eggs, especially for the children who want to touch them. We will be more careful from now on in monitoring the exhibits," said Toshiki Hori, the curator of the pavilion.

The Japan Expo 2001, which opened in July, runs through Nov. 4.