Police in Los Angeles were searching on Wednesday for two women observed via security cameras taking a plastic-coated human fetus from the traveling “Body Worlds” exhibit at the California Science Center over the weekend.

The 13-week-old “plastinated” fetus was part of Gunther von Hagens’ popular and controversial “Body Worlds 2: The Anatomical Exhibition of Real Human Bodies.”

Von Hagens, a German anatomy professor, preserved 200 donated human bodies and body parts by replacing body fluids with plastics, then placing the skinless forms in sometimes whimsical poses.

The fetus, which had been in an unlocked case, was a taken early on Saturday morning while the science center was open around the clock to accommodate crowds on the last day of the exhibit, police said.

More than 16 million people worldwide have viewed the traveling exhibits. The theft was the first associated with the exhibits, Los Angeles police said.

The exhibit closed in Los Angeles at midnight on Sunday.