A newborn baby was discovered dead inside a portaloo in a shocking find at an American music festival that police have since declared a homicide.

The cleaning crew at Electric Forest in Michigan came across the baby during routine maintenance on Sunday morning, according to Michigan State Police.

The force revealed that the infant was found in the toilets within the festival's camping area and was believed to have been born inside the portaloo, as the placenta and umbilical cord were allegedly also present, reports News 8.

The outlet confirmed that the baby had been born alive and breathing, with fluid found in its lungs and stomach.

Michigan State Police Lieutenant Pat Agema confirmed that the death of the newborn has been classified as a homicide. An autopsy was completed on Wednesday with the official report still pending.

The identity of anyone potentially connected to the child has yet to be announced.

Thousands of attendees had been camping at the grounds near Lake Michigan at the festival from Thursday.

Police said in a statement: "The Michigan State Police continue to investigate the discovery of a deceased neonate found Sunday morning in the camping area at the Electric Forest Festival. Investigators are asking for the public's assistance.

"If you were in the area and observed anything unusual, or if you have information that you believe may be relevant, we encourage you to come forward.

"We appreciate the public's cooperation and ask that people avoid speculation on social media out of respect for the investigation and those affected."

One festival-goer posted on Reddit that they awoke on Sunday morning to find police on the scene, with no knowledge of what had taken place.

They wrote on Sunday: "This happened right by us at the Electric Avenue preset tents. We got up this morning to head out of the fest and there were about six-eight cops, four cop cars and a bunch of security/EF staff parked right around two cordoned off porta potties.

"We didn't know what was going on but figured something bad happened. But this is horrifying.

"My girlfriend used those same bank of porta potties at around 6am and could've been unlucky enough to have gone in one of those. So sad."

A separate user wrote in a since-deleted post that they had spotted the baby but believed it to be a doll at the time.

The post read: "I went into the porta potty and was about to sit down but glimpsed what was apparently an infant's face.

"I was confused for a second, but honestly I thought it was a doll. People always bring weird s*** to festivals and it never occurred to me it was an actual body.

"After I read the report, it clicked.

"I now live with this crazy amount of guilt. Maybe if I took it seriously and reported it earlier that baby would still be alive? I'm very traumatized though and I won't be going to any music festivals or porta potties for a long time."

In an online statement, Electric Forest wrote: "Forest Family, it causes us so much pain to have to share this difficult news with you. Michigan State Police continues to investigate this tragic event if you can assist in any way. HQ is heartbroken and knows that our Forest Family is as well."

Despite the tragedy, the festival posted a message at the close of the event celebrating 'another stunner', prompting furious festival-goers to brand the organisers 'tone deaf'.

One user said: "Crazy how the biggest headline of this place is about a dead baby in a porta potty yet you're like "wow another great year," shut this s*** down forever".

Another slammed the festival for being 'out of touch,' with numerous others also describing the response as 'tone deaf. '.

Officers have appealed for members of the public to come forward with any information that could aid their investigation.

Disturbingly, this was not the only horrific incident to blight Electric Forest during the event, which was also marred by a number of deaths following a car crash and a suicide.

Jerard 'Jay' Jackson, 28, was reported missing after he was last seen departing the festival on Monday morning. On Tuesday at around 3.30pm, authorities found Jackson's body and said he had hung himself.

Michigan Police also confirmed that a car crash was connected to the festival, with a third individual still unaccounted for.

The Express has contacted Electric Forest for further comment.