By 26 May 2010, over 130 lawsuits relating to the spill had been filed[332] against one or more of BP, Transocean, Cameron International Corporation, and Halliburton Energy Services,[333] although it was considered likely by observers that these would be combined into one court as a multidistrict litigation.[333] On 21 April 2011, BP issued $40 billion worth of lawsuits against rig owner Transocean, cementer Halliburton and blowout preventer manufacturer Cameron. The oil firm alleged failed safety systems and irresponsible behaviour of contractors had led to the explosion, including claims that Halliburton failed to properly use modelling software to analyze safe drilling conditions.[334] The firms deny the allegations.