The road blocked by Khan's supporters, in Khyber Pakhtunkhwa province, leads to one of two routes used to ship NATO supplies to Afghanistan.
Companies have also mostly stopped sending trucks to the second crossing in southwest Baluchistan province, Shah said. Officials will review the situation on Wednesday and decide whether to let the trucks move, he said.
Imran Khan's Tehreek-e-Insaf party, which controls the Khyber Pakhtunkhwa government, pledged on Saturday to block NATO shipments until the U.S. ends drone attacks targeting Islamic militants in northwest Pakistan. Protesters stopped trucks and roughed up drivers on Sunday on the outskirts of Peshawar, the capital of Khyber Pakhtunkhwa, before the police stepped in.
Covert CIA drone strikes in Pakistan have long been a sensitive subject, with officials regularly criticizing them in public as a violation of the country's sovereignty. The issue is more complicated, however, since the government is known to have supported at least some of the attacks in the past.
The federal government has also criticized drone strikes but has indicated it has no interest in blocking the NATO supply route, which could spark a crisis with the U.S. and other NATO countries. The police actions Monday indicated that the federal government had intervened to stop the NATO blockade.
The land routes through Pakistan have been key to getting supplies to NATO troops in Afghanistan. They now increasingly are being used to ship equipment out of Afghanistan as the U.S. seeks to withdraw most of its combat troops from the country by the end of 2014.
The routes have been closed in the past. The Pakistani government blocked the routes for seven months following U.S. airstrikes that accidentally killed two dozen soldiers on the Afghan border in November 2011. Pakistan finally reopened the routes after the U.S. apologized.
Also Tuesday, militants freed seven teachers who were kidnapped last week in the northwest Khyber tribal area while working on a polio vaccination campaign, said local government official Shabir Ahmed Khan. The teachers were released after tribal elders held discussions with the militants, Khan said.
Militants have killed more than a dozen polio workers and police protecting them over the last year in Pakistan, one of only three countries where the virus is still endemic. They claim the workers are spies and the vaccination is meant to make Muslim children sterile.
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Associated Press writer Riaz Khan contributed to this report from Peshawar.