Police used a Taser stun gun as they arrested a man suspected of having a firearm.
Police were called to the house on Ayr Way, in Romford on the east London/Essex border, at 2010 BST on Monday.
Reports suggested the man had a firearm but nobody has been injured.
Police used the Taser during the incident. The man was unharmed and was taken into police custody where he will be questioned later.