Emily Suzanne Cain (pictured) was indicted by federal authorities for allegedly attempting to mail three human fetuses from Colorado to the U.K.

A Colorado woman has been indicted for allegedly attempting to mail three stillborn human fetuses from the 1920s to the UK.

Emily Suzanne Cain, 38, of Fort Collins appeared in San Francisco federal court on Wednesday afternoon after pleading not guilty on Tuesday.

Cain was arrested after customs agents scanned the package and were horrified to find three 'wet specimens' of human fetuses - which had been labelled as 'school teaching aids and t-shirts.'

Police say she'd been able to get her hands on the fetuses through a friend who worked at a university biomed lab.

The lab was downsizing so they were getting rid of some of their specimens.

Cain had then posted an ad on Facebook offering to sell the three wet specimens and one dry fetal skeleton for $20,000.

She was caught when attempting to ship three of the fetuses to a buyer in Westminster in England on October 15, 2018.

She had shipped the package from Cañon City, Colorado, but Customs and Border Protection officers in San Francisco flagged it before it could be loaded onto a London-bound flight, 9 News reports.

Customs agents noticed that an important form - which certifies the package is not dangerous - was not signed by Cain prior to shipping. When they sent it to be x-rayed they saw objects that 'appeared to be a human shape.'

Inside custom agents found three glass containers allegedly holding three human fetuses.

The package also contained a hand-written letter from Cain apologizing for the delay and offering the recipient a free t-shirt.

The t-shirt was printed with a picture of a 'Purgatory Museum' and the phrase 'Real Shrunken Head.'

The card had the name: 'G. Howard McGinty Director and Curator of McGinty Fine Oddities' on it.

According to the company's website, McGinty Fine Oddities appears to have peculiar objects like shrunken heads, wet specimens, mummies and skeletons among other objects.

Authorities found finger prints for Glenn McGinty of McGinty Fine Oddities in the UK, a curator that has objects like shrunken heads, were found on the package

Afterwards, the remains were collected by the San Mateo County Coroner's Office for further examination and the remains were confirmed as human fetuses.

After the initial discovery, fingerprints were found on the box belonging to Cain and Glenn McGinty.

During this time, Cain contacted the USPS customer service line on October 30 from Colorado.

She asked why her package was being held in San Francisco and told the phone teller that the package's recipient was 'getting a little antsy.'

Cain (pictured), who allegedly tried to sell four specimens on Facebook for $20,000, was arrested and released on a $5,000 bond

Cain called USPS customer service three days later to once again check on her package's status.

Meanwhile, investigators were able to search Cain's Facebook and discovered she tried to sell the specimens on her Facebook page prior to the incident.

Cain 'informed another Facebook user that she recently acquired a collection of three fetal wet specimens and one fetal skeleton wet specimen from a university lab collection,' according to 9 News.

The post allegedly contained seven photos and explained she would sell all four specimens for $20,000.

Cain posted on her Facebook: 'We don’t always post publicly. Especially with pieces like these ...' and '... too controversial to be up everywhere, for everyone to see. I try to keep them for the special clients and others we know may have interest in them.'

She gained access to the university lab, revealed to be the Department of Medical Education at Creighton University in Omaha, Nebraska, through a female friend who was head of the biomed department.

She picked up the fetuses from a U-Hail trailer.

University officials said their policy is to cremate, not sell specimens, and that they are cooperating with federal officials.

Cain was arrested by authorities in Fort Collins and released on a $5,000 bond.

For her crime she will potentially be charged under U.S. Code § 289g–2, which says it is unlawful to 'knowingly acquire, receive, or otherwise transfer any human fetal tissue for valuable consideration.'

Cain has been required to wear a GPS monitor.

DailyMail.com contacted Cain's attorney for further comment.