Police are searching for two women who they believe made off with a preserved 13-week-old fetus from an exhibit at the California Science Center (search).

The fetus, infused with polymers in a process called plastination to prevent decay, was part of a traveling display entitled "Body Worlds 2: The Anatomical Exhibition of Real Human Bodies." (search)

A surveillance video showed the suspects removing the fetus from an unlocked display case on the third floor between 2 a.m. and 3 a.m. Saturday during the round-the-clock closing weekend of the exhibit, police Detective Jimmy Render said Tuesday.

Other people were inside the room during the heist but may not have been aware of it, he said.

"There's no indication at this time of the motives behind the stealing of the plastinated fetus. ... There had been no threats," the detective said.

"Body Worlds 2" and its predecessor, "Body Worlds," use plastinated human bodies and organs to provide information on human anatomy, illnesses and issues such as smoking and obesity. The displays, which feature bodies in natural or whimsical poses, such as playing chess or riding a skateboard, have drawn critical and public praise.

The theft was the first ever involving the "Body Worlds" displays, which have been seen by millions of people worldwide, and by about 875,000 at the California Science Center alone. It also was the first from the science center since it opened in 1998, the museum said.

"We are deeply concerned and disappointed by the theft of this invaluable and irreplaceable specimen," Angelina Whalley, director of the Institute for Plastination (search), said in a statement.

"How can somebody do this ... it's such a disrespect," she said.