A Pakistani judge has ordered the arrest of the driver of a US embassy vehicle which killed a bystander at the scene of a shooting by a US official.
The vehicle is said to have struck Obaidur Rahman on its way to assist Raymond Davis after he shot two men he says were trying to rob him in Lahore.
Mr Davis is being held in jail pending a decision on his diplomatic status.
The court order comes after Mr Rahman's family filed a petition demanding the driver's arrest.
Pakistani authorities have already asked for the embassy vehicle and its driver to be handed over - but the US has yet to comply with this request.
The case has soured relations with the US and become a highly emotive issue in Pakistan.
Correspondents say the government is under tremendous domestic pressure to put Mr Davis on trial despite US assertions that he has diplomatic immunity. Mr Davis is charged with two counts - murder and possession of illegal weapons.
Hundreds of Pakistanis have taken part in street demonstrations.
The death of Mr Rahman as an innocent bystander has only served to intensify public anger, particularly as the details surrounding the circumstances of his death are unclear.
The BBC's Syed Shoaib Hasan in Karachi says that witness reports and investigations seem to contradict early assertions that the second car rushed to the scene to rescue Mr Davis.
Our correspondent says that subsequent investigations have now shown that the vehicle - a Toyota Land cruiser - was with Mr Davis at the time of the incident. In fact, according to eyewitnesses, Mr Davis was leading and clearing the way for the Toyota when the incident took place.
Friday's Lahore High Court order directs the regional Punjab government to "take all necessary steps under the law to investigate this case," Asad Manzoor Butt, the Rahman family lawyer told the BBC.
The family claimed that no investigation was conducted by the police and no effort was made to recover the consular vehicle and arrest the driver.
Although the court order directs the Punjab government to launch an investigation, the case is being handled by federal authorities.
Indeed there appears to be a divide between the government of Punjab province - where the killings took place - and the central government as to who is responsible for ascertaining the diplomatic status of Mr Davis.
On Thursday a Pakistani court delayed until 14 March any decision on whether Mr Davis has diplomatic immunity after Pakistani officials argued for more time to prepare their case.
The decision came after US envoy John Kerry vowed Mr Davis would be subject to a criminal inquiry at home if freed. He met President Asif Ali Zardari in a bid to defuse tensions over the issue.
Earlier US President Barack Obama weighed in saying that Mr Davis should have diplomatic immunity. The president said it would be untenable if diplomats were prosecuted.
As more allegations about what happened emerge, correspondents say that it looks increasingly like a formula to keep all sides happy simply does not exist.