Three police officers feared for their sight after they were sprayed with a chemical which can cause blindness during a drugs raid.

The officers were splashed in the face with ammonia after forcing their way into a flat in Adelaide Road, Chalk Farm, at 6.50am on Friday.

Det Sgt Richard Greenwood, who took part in the raid but was not sprayed, said: “People didn’t realise what it was. It’s painful and people thought they had been blinded. They were very scared.”

The officers were treated at the scene by paramedics, who washed out their eyes, and then taken to hospital.

Fortunately, they escaped serious injuries and all three have since returned to work.

Det Sgt Greenwood, who is based at Kentish Town police station, added: “I have never had that happen before and I’ve been in the police for nearly 25 years.”

Two people at the property, who were suspected of dealing heroin, were also taken to hospital after one inhaled ammonia and the other sustained injuries as he resisted arrest.

A spokesman for government body Public Health England said the chemical, used in fertilisers and cleaning products, can cause sight loss in extreme cases.

She said: “Short term inhalation can result in irritation of the eyes and nose, a sore throat, cough, chest tightness, headache and confusion.

“Skin exposure can cause serious burns and ingesting it can result in burns to the mouth and throat.

“Splashes in the eye can cause damage which may be irreversible and lead to loss of sight.”

A 57-year-old man was held at the scene on suspicion of assault on police officers.

He has been placed on police bail until October.