Clubbers in London’s Tiger Tiger were mistakenly given caustic soda instead of salt when knocking back tequila slammers, sending four people to hospital with burns.

Police attended the nightclub near Piccadilly Circus in central London last month after receiving reports that people had chemical-related injuries, believed to be caused by a staff error. Authorities then closed Tiger Tiger as a precaution.

A Metropolitan police spokesperson said: “Police were called to Tiger Tiger at approximately 10.50pm on Tuesday 7 December following reports of four people who had suffered burns after coming into contact with a substance, believed to be a strong alkali, at a venue in Haymarket.

“Four females received treatment at the scene before being taken to hospital. None of their conditions are life-threatening. A fifth person, a male, also came into contact with the substance but has declined hospital treatment.

“The incident is not being treated as suspicious and there have been no arrests. The Health and Safety Executive has been informed.”

Caustic soda, or sodium hydroxide, is an alkali often used in soap and paper production and in powerful cleaning substances.

The Haymarket venue, known for its Ibiza-inspired party rooms, is operated by the British hospitality group Novus Leisure, which owns 41 bars, restaurants and nightclubs in cities across the country.

A shot of tequila is made into a slammer by licking salt first and then sucking a lime or lemon after.

A source told the Sun: “A group of four women and a man necked the tequilas and used salt and lemon to soften the taste, then began to retch. One girl keeled over. Despite music blaring, everyone knew something was wrong. There was panic. People thought it was some kind of terrorist incident. It took a long time to establish what happened.”

According to the Sun, one of the victims is still requiring hospital treatment more than a month after the incident. Tiger Tiger and Novus were contacted for comment.

A Met police spokesperson said the force was not aware of any similar incidents in London, but said they were not always referred to the police and may instead go to the Health and Safety Executive or emergency services.

The Health and Safety Executive did not respond to a request for comment.

Novus was listed for sale by its private equity owner, Hayfin Capital Management, in 2018. David Cameron had been a non-executive director for the chain when it was briefly listed on the London stock exchange in 2005 under the name Urbium.