Militants in north-west Pakistan have abandoned 12 trucks they hijacked a day earlier, local officials said.
The trucks were emptied of their contents and left in a valley. There is no word yet on the fate of the drivers, reported BBC.
The trucks were carrying supplies for Western forces in Afghanistan. They were stopped on Monday as they travelled through the Khyber Pass.
The road is a major supply route for US and Western forces battling against the Taleban in neighbouring Afghanistan.
Hauliers say that over 350 trucks daily carry an average of 7,000 tonnes of goods over the Khyber Pass to Kabul.
The trucks were seized at four places along a 20-mile (35km) stretch of the road, officials said.
They said about 60 masked gunmen took away the trucks with their drivers.
"The containers have been released. They were abandoned in a valley. They are empty," a local official in the Khyber Agency tribal area said.
It was not clear what goods were the trucks transporting. The fate of the drivers is yet to be known.
Pakistani officials have blamed the hijacking on militants loyal to the Taleban commander Baitullah Mehsud.
Security along the road leading to the border has deteriorated this year, correspondents say, with soldiers recently carrying out an offensive in the Khyber region to drive militants away from the outskirts of Peshawar, the main city in the north-west.
Traders in the main town before the pass, Landikotal, complained that the government was not providing adequate security on the road.
About 24 trucks and oil-tankers have been attacked in the past month, transport operators said.
Last year, Sawab Khan, a member of the truckers' association, told the BBC that goods transported include supplies for Western forces fighting the Taleban, as well as supplies for non-governmental organisations, the government and Afghan traders.
Mr Khan said that in addition to the threat caused by militants, every truck pays about 400,000 Pakistani rupees (about $5,000) annually in taxes and bribes.
Truckers who refuse to pay bribes are often made to park along the road and wait, sometimes for more than 24 hours, before they are allowed to move on, he said.
Some truckers also complain of extortion on the Afghan side of the border.
Supplies to the southern Afghan provinces of Kandahar and Herat pass through Quetta and across the Chaman border in the Balochistan province of Pakistan.
The truckers operating on this route say they confront fewer problems.