A mystery smell so powerful that it woke people up wafted across at least two Top End neighbourhoods early yesterday.

Theories about the source of the stink ranged from sewage to the exhaust fumes of an alien spaceship.

Keith Risk, 47, of Howard Springs, said the stench woke him up about 3am.

"It was overpowering," he said. "Like gas or rotten eggs. I drove around nearby streets and could still smell it.

"The stink went on for kilometres."

He said the smell could have been caused by sewage, gas or even flowering trees.

Mother-of-two Gina Francis, 41, of Marlow Lagoon, Palmerston, said her whole household was woken by the pong.

"I thought it might be a gas leak and was worried," she said. But her husband Rod thought it more likely to be a chemical spill.

Police said there had been no reports of chemical accidents.

And the firies said there had not been any reports of gas leaks.

Mr Francis telephoned police and they said there had been many calls about the strange smell.

Litchfield Shire Council president Mary Walshe suggested there had been an accident at a clandestine amphetamine laboratory.

But police said "clan labs" always smelt. "That's why they are set up in remote areas," an officer said. "But the smell only goes for a property or two."

A reader blamed the Litchfield rubbish dump, but Ms Walshe said the dump was innocent.

Independent politician Gerry Wood said the source of the smell may never be known. "We've had plenty of UFOs around here," he said. "This is a USO - Unidentified Smelly Object."
Super 7 Theories
1. Secret chemical spill
2. Clandestine drug laboratory
3. Flowering trees
4. Gas leak
5. Palmerston sewerage plant
6. Overflowing cesspits in rural area
7. Exhaust fumes from a visiting UFO