Two people were taken to hospital as a precaution as detectives investigated a suspect package at Britain's parliament, police said in a statement.
"Specialist officers are in attendance and the package is being assessed," the statement said on Monday (local time).
"London Ambulance Service attended and two people, a man and a woman, have been taken to hospital as a precaution."
A spokeswoman for the parliament added: "We are aware of a potential situation involving a suspicious substance which the Met Police are investigating.
"There has been no evacuation, but the affected area has been cordoned off."
Last month, police investigated white powder sent to an office in parliament, which was later found to be harmless.