"Specialist officers have been called and the package will be assessed", they said, and no one is thought to be injured.
Two people were taken to hospital as a precaution as detectives investigated a suspect package at Britain's parliament, police said in a statement.
Police were called to the estate where MPs and their staff have their offices on Tuesday at 9.49am. A man has been taken to hospital as a precaution'.
Henry Zeffman, political reporter at The Times, tweeted that the package is understood to have been sent to Rupa Huq, MP for Ealing Central, prompting offices to be evacuated.
The package was sent to Muslim Labour MP Mohammad Yasin, according to local media reports.
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A parliamentary spokesman confirmed four packages had been sent to the building in recent days and said police were investigating the latest package.
Several ambulances from the Incident Response Unit are on the scene. We can not provide any more details at this stage.
Two were sent to Portcullis House and Norman Shaw Buildings on Monday, both of which were later deemed non-harmful.
"Police are investigating the content of the letters to identify any potential links".
The affected area was temporarily cordoned off but there was no evacuation of the Norman Shaw Buildings, which are situated between the Houses of Parliament and police headquarters, the parliamentary spokesperson said.
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