ISLAMABAD: Pakistan on Tuesday conveyed its concerns to India over delay in the free and fair investigation of the attack on Samjhota Express, said a statement issued by the Foreign Office.

“Pakistan has conveyed its grave concern to India over unnecessary delay in the free and fair investigation of Samjhota Express terrorist attack in which more than 42 innocent Pakistani nationals lost their lives,” said the statement.

The Foreign Office added that India's attempts to exonerate certain individuals involved in the attacks have raised serious questions over the due process of law and dispensation of justice.

Islamabad in 2015 had protested India's decision to not oppose bail for the prime accused in the case.

“The Government of Pakistan expects India to take steps to bring to justice all those involved in the heinous act of terrorism on the Samjhota Express," the Pakistan foreign ministry had said.

Pakistan also suspected the involvement of Lt Colonel Prasad Purohit, a serving Indian Army officer, in the Samjhota Express blasts.

In 2008, the Maharashtra Anti-Terrorism Squad had revealed that Purohit supplied the RDX used in the Samjhota Express bombing.

In February 2007, alleged Hindu extremists had bombed the Samjhota Express, killing 68 people, 42 of whom were Pakistanis.

The explosions ripped through the train during its transit through Panipat on its way to Lahore from Delhi.