Knesset Speaker Yuli Edelstein instructed Knesset Security Chief Yosef Griff to allow the police to enter Ghattas's office in order to search it.
Police officers were accompanied by Griff and Knesset Legal Adviser Eyal Yinon to ensure that police only review or take documents relevant to their investigation. Any item about which the sides disagree must be put in a closed envelope and brought to a court to decide.
On Thursday, Ghattas gave up his immunity from search and arrest, after the Knesset House Committee voted to strip him of it.
The only other MK to ever have his office searched was Ghattas' cousin and Balad founder Azmi Bishara in 2007. Bishara fled the country while under investigation for giving information to Hezbollah during the Second Lebanon War.