LONDON (Reuters) - A Thai restaurant's potent homemade chili sauce caused a chemical scare in central London, with police shutting streets and firefighters forced to smash down the door.

Streets were cordoned off outside the Thai Cottage restaurant in London's Soho theatre and nightlife district.

"It was initially thought to be a chemical problem. Somebody smelled what they thought was chemicals. So we went there, cordoned it off and assisted the fire brigade," a police spokesman said.

The ambulance service dispatched a Hazardous Area Response Team unit to Monday night's alarm.

Firefighters dressed in special suits broke down the doors and discovered the source of the smell: chef Chalemchai Tangjariyapoon's fiery signature nam prik pao chili sauce.

The chef was baffled by the commotion. "I was making a spicy dip with extra-hot chilies that are deliberately burnt. To us, it smells like burnt chili and it is slightly unusual," he told the Times newspaper.

"I can understand why people who weren't Thai would not know what it was. But it doesn't smell like chemicals."