Prosecutors in Chicago have added four defendants to a case involving planning for the 2008 terrorist attacks in Mumbai, India that killed 164 people.

The four, Sajid Mir, Abu Qahafa, Mazhar Iqbal and a man known only as "Major Iqbal" are charged with conspiracy to murder and maim people in India and with six counts of aiding and abetting the murder of U.S. citizens in India. None of the men added to the case are in custody.

Co-defendant Tahawwur Hussain Rana faces a May 16 trial date. Last year, David Coleman Headley, an American of Pakistani descent, pleaded guilty to charges he helped plan the Mumbai attack by scouting the targets for the terrorist group Lashkar-e-Tayyiba and of scouting a proposed follow-up attack on the Danish newspaper Jyllands-Posten. Mir also was charged in connection with the Danish plot.

Headley is expected to be a prosecution witness at Rana's trial. A federal judge has ordered that Rana cannot argue his actions were "an exercise of public authority on behalf of the government of Pakistan" via its intelligence service, the ISI. The Indian government believes the ISI was involved in the plot. In new cables released by Wikileaks, U.S. government officials in 2007 listed the ISI among foreign terrorist groups

Rana is accused of helping facilitate Headley's surveillance missions and of serving as a communications conduit for "Major Iqbal."

For more, see the second superseding indictment here.