MOTORISTS looking out for traffic lights got a shock in St Clair on Wednesday when they spotted a pig's head peeking out from where an orange light should have been.
Police were called to Banks Dr about noon and quickly removed the head, with no motivation yet known for the prank.
One motorist Laura Alcorn said she hadn't noticed the gruesome scene until her young son pointed it out.
"My very observant son said, 'What is that in the traffic light?' I said, 'Must be a stuffed animal'," she said. "As we turned I caught a better glimpse and said, 'Nope that's a pig's head'."
Ms Alcorn said the pair returned to the lights hours later on to see if the head was still there - it was.
"[My son] was very amused until the smell hit us. It was horrid," she said.
Ms Alcorn called Penrith Council and then Roads and Maritime Services to report her discovery.
She wasn't believed at first but eventually convinced RMS to send out staff to inspect the site.
"You could just put an apple in its mouth and it would be a perfect picture," Ms Alcorn said.
A spokeswoman for NSW Police said an investigation was underway.
Anyone with information should call Crime Stoppers, 1800 333 000.