The security alert, reportedly sparked by a letter sent to a peer containing white powder, lasted for an hour and a half before police declared the incident over.
"The incident has been stood down. It was a suspicious package that had been delivered to the Houses of Parliament," a spokeswoman for the Metropolitan Police said. "There are no reports of any injuries or illnesses."
Shock attack: British MP killed ahead of EU vote
A Lords spokesman had said earlier that parts of the building, including the car park and terrace overlooking the River Thames, were closed "due to a potential security issue that is being investigated".
He later said: "It's over. The investigation found that there wasn't any security threat and so the closed areas were re-opened."
Matt Chorley, a reporter for The Times newspaper who was on the terrace at the time, had tweeted that police were investigating a "chemical incident".
"Letter to a peer being analysed by police over white powder in envelope," he said. Neither police nor the House of Lords would immediately confirm his account.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ