Northern Irish First Minister Peter Robinson has stepped down from his position after a bid by his party, the DUP, to adjourn the assembly, failed.
The DUP failed to get enough support to adjourn the assembly, after Sinn Féin, the Ulster Unionists and the Social Democratic and Labour Party (SDLP) voted against the adjournment motion.
The crisis started with the murder of a former IRA man and a police assessment that IRA members may have been involved.
Mr Robinson said the latest problems have "pushed devolution to the brink".
Kevin McGuigan Sr was murdered in Belfast last month but the political row escalated on Wednesday, when detectives arrested a senior member of Sinn Féin as part of the murder inquiry.
The party's chairman in Northern Ireland, Bobby Storey, is still being questioned.
DUP says no more meetings of NI Executive, after killing of former IRA man (07 September 2015)