© Leilani Hatch/Manawatu StandardPalmerston North's "big bang" has police and Fire Service puzzled.
"It was a definitely a loud deep bang - nothing like a gun shot bang, which is quick and high pitch.
Palmerston North Astronomical Society member Noel Munford said the noise could have been a sonic boom created from a fire ball.
But he said if it was a fire ball, then there would have been reports of people seeing a "bright light", burning space junk, shooting across the sky. Gail Lucinsky said she heard the explosive sound from the bottom of Pahiatua Track.
"It was so loud that I jumped out of my skin thinking that one of my parents had fallen heavily and hit the wall in the room behind me."
She said she went outside to look for a source but could not find anything.
"A transformer exploding was suggested as a likely cause, but we couldn't see any part of Palmy in darkness, so it remained a mystery," she said.
Sofia Butler said she heard the explosion sound "very loud and clear" from Lombard St.
"I also heard lots of teens roaming around the streets which at the time I thought may be responsible for that big bang. I haven't heard anything like it to be fair."
Suzanne Phibbs said she and her neighbours heard the noise from Limbrick Street in Terrace End.
"It was loud and shook the house."
Geoff Bethell said he heard the bang from Milverton Park.
"I heard a very loud bang sometime last night but, being me, didn't give it a second thought .... It was so loud I thought it was nearby and just a few drunks setting something off in Milverton Park."
"If it was so loud all over Palmerston North I'd have to suggest a very small fireball either coming down to earth or exploding as an air-burst over the city," he said.
Wayne Sio was woken by the noise.
"The wife and I were sound asleep and woke up instantly it was so loud, and it actually felt like the house vibrated.
"We are in the Milson area near the airport and thought something must have happened at the airport," he said.
The Milson fire service attended a call to Kelvin Grove after residents complained about a loud explosive bang. But Palmerston North central senior station officer Graeme Mills said nothing was found by the fire service. They had been in touch with a power company on Thursday night to see if any outages had been reported.
A Powerco spokesperson said there were had been no reports of any bangs or any equipment failure at that time in Palmerston North. A Defence Force spokesperson said the army were not responsible or related to the noise.
"No, it wasn't us."
The police spokesperson said they would continue to look into the situation if more information came to light.
Wow, someone should make a television show about the theory behind this big bang. Any ideas on a catchy name?