Police on Monday found explosives on a road close to the home of former military ruler Pervez Musharraf, two days before he is to appear before a treason tribunal.
The 2.5 kilos (5.5 pounds) of explosives and two detonators were found around two kilometres (1.2 miles) from the retired general's home on the edge of Islamabad.
The discovery was made close to where five kilos of explosives were found last Tuesday, as Musharraf's treason trial was due to start.
The case was adjourned to Wednesday because of the security alert.
The treason allegations are the latest in a series of serious criminal charges relating to Musharraf's 1999-2008 rule, brought against him since he returned from exile in March.
"We have found five packets of explosive material, each weighing half a kilo, with two detonators," police chief for Bani Gala, Abdul Rauf Kayani, told AFP.
He said the material was found on the central reservation of Park Road, the main road leading to central Islamabad from the leafy suburb where Musharraf lives.
"It is not clear who put the packets here but we have impounded them and begun an investigation," Rauf said.
Musharraf said Sunday he had not yet decided whether to attend Wednesday's hearing, at which the charges against him are to be read out.
On Sunday he denounced the case as a "vendetta" against him, and said he had the backing of the country's powerful army.
"I have no doubt with the feedback that I received that the whole army is... totally with me on this issue," Musharraf told reporters at his farmhouse on the edge of Islamabad.
The 70-year-old returned to Pakistan to run in May's general election -- won by Sharif -- after several years of self-imposed exile.
But he was barred from running and hit with a series of criminal cases dating back to his time in office.
These include murder charges over the assassination in late 2007 of former prime minister Benazir Bhutto, as well as charges over the death of a rebel leader, a deadly military raid on a radical mosque and the detention of judges.