The Philadelphia Police Department has launched an investigation after the Mütter Museum received an unusual package Tuesday morning.

Police said around 11:36 a.m. Tuesday, museum staff reporting receiving a package containing two preserved fetuses in a glass jar. Police said they immediately launched an investigation to determine the source of the package.

"I opened it up. There was a letter there that said this was a retired physician and he or she was saying they had these two specimens and that's basically it," museum curator Anna Dhody said according to CBS News.

Dhody told CBS News that when it comes to donations, there's a whole process that goes into it and nothing is ever just dropped off at the museum like this. She said the package was specifically addressed to her and didn't include a return address.

Two bottles with 'very small fetal remains'

"But there was no identifying information. They just identified themselves as a retired physician. There were two bottles with fluid and inside that there appeared to be two very small fetal remains," she told CBS News.

"I have been here for almost 20 years and I have never received human remains anonymously in the mail," Dhody told NBC 10 Philadelphia. "This was definitely out of the ordinary."

The fetuses have been turned over to the medical examiner's office for further investigation, according to a news release from Philadelphia police.

Museum contains anatomical specimens, medical instruments

Anyone with information is encouraged to contact the Central Detective Division at 215-686-3093 or call or text the PPD tip line at 215-686-TIPS (8477).

The museum, located in Philadelphia's Center City West neighborhood, is run by the College of Physicians of Philadelphia and displays "beautifully preserved collections of anatomical specimens, models, and medical instruments in a nineteenth-century 'cabinet museum' setting," according to its website.

The museum says its goal is to help visitors understand the mysteries and beauty of the human body and appreciate the history of diagnosis and treatment of disease.