By Syed Shoaib Hasan
BBC News, Karachi
Mr Mallah is one of hundreds of Pakistani people who have disappeared
Pakistan's Supreme Court has ordered the powerful ISI intelligence agency to appear in court to explain what has happened to a missing political leader.
Akash Mallah went missing in October 2009 in the city of Hyderabad in the southern province of Sindh. He is believed to be held by the ISI.
Pakistan's security agencies routinely detain such suspects for "anti-state" activities.
Most are held without being charged for months and even years.
The Supreme Court has already ordered the government to set up a national commission to investigate what has become a major humanitarian crisis.
"We have given you adequate time and the officials must now appear in person," the judges said in their remarks on Thursday in the southern city of Karachi.
The hearing was being held to examine a report submitted by the local police, who investigated the case on the directions of the court.
The police clearly stated that Mr Mallah had been arrested by ISI officials.
This is the second time that the deputy head of the JSQM, an ethnic party based in Sindh province, has been detained.
He was also held in 2006 for 18 months before being released without being charged.
His case is just one of hundreds being heard in the Supreme Court.
Most of those arrested belong to nationalist groups in southern Sindh or Balochistan provinces, and some are said to be members of jihadist organisations.
Human rights groups maintain that such detentions have been used to intimidate nationalist groups.