Cooking flour sent from Sri Lanka caused a security alert at Sutton sorting office this morning.
Police were called to the depot in Grove Road after post office sorting staff intercepted a package containing suspicious white powder.
Some deliveries were delayed by nearly an hour as Met officers trained to deal with hazardous substances attended the scene.
The substance found in the mail from Sri Lanka to an address in Sutton was found to be non-toxic and the all-clear was given shortly after 10am.
An inside source said the substance turned out to be cooking flour.
A spokesman for Sutton Police said officers and Post Office staff would visit the address marked on the package.
London Ambulance Service and London Fire Brigade also attended but no one was injured in the incident.
An LAS spokeswoman said an ambulance, duty officer and three units from its Hazard Area Response Team were sent to the site after a call from police at 8.45am.
"A package was found to be leaking powder at Sutton Delivery Office this morning.
"It was isolated and dealt with according to our normal procedures.
"It turned out to be a harmless substance. There were no significant delays to mail deliveries," said a Royal Mail spokesman.
- Do you know who the flour was sent to? Contact the newsdesk on 020 8330 9542.
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