Four police officers have been treated for chemical exposure after they raided a suspected drug lab at a house in Sydney's inner west.

Police say they have had the home on Pile Street Dulwich Hill under surveillance for some time, and last night found a large amount of chemicals at the house.

Acting Inspector Alex De Brouwer says four officers complained of feeling ill after entering the scene.

"They showed signs of a chemical reaction, so we thought we'd err on the side of safety and we called in the drug squad chemical operations unit," he said.

"They then attended a short time later, conducted some tests and there was nothing conclusive found."

Paramedics attended to the officers.

The chemicals found in the house are still being tested and police are looking for the occupants.

Anyone with information can call Crime Stoppers on 1800 333 000.