Three people were injured after an envelope containing a "substance" was delivered to a business in London's Borough Market.
Police, paramedics and firefighters were all called after the package was discovered at Feng Sushi in Stoney Street at about 13:40 BST.
The building was evacuated as a precaution but Scotland Yard said it was not treating the incident as terror-related.
No arrests have been made.
The three people all suffered minor injuries "as a result of an irritant" and were treated at the scene by London Ambulance Service.
Police said the substance had been identified as "naturally occurring".
Local businessman Paul Dawson said he had been told by a community warden that "a white powder had been received" by the business.
He added the restaurant manager had said to him he had to close his shop because "something quite bad had happened".
The property was one of the locations targeted in the terror attack in June.