Peshawar, Pakistan (CNN) -- Seven teachers abducted last week for supporting a polio vaccination campaign in Pakistan's tribal Khyber Agency have been released by militants, their school principal said Tuesday. "All the teachers have been released after they were questioned over their activities by militant group Lashkar-e-Islam," Hira Public School Principal Qasim Khan told CNN. The principal would not say what information the militant group wanted from the teachers, who were abducted Thursday. The militant group, which has connections to the Pakistan Taliban, opposes polio vaccinations, accusing polio workers of pursuing a political agenda. Anti-polio campaigns have been targeted by militants in Pakistan since U.S. intelligence officials used a fake vaccination program to help in their hunt for Osama bin Laden in 2011. Under cover of the program, the CIA sought to collect DNA samples from relatives of the al Qaeda leader to verify his presence in a compound in Abbottabad. Since July 2012, at least 22 polio workers have been killed. The polio campaign has a history of controversy in Pakistan. Some mullahs have preached against it, claiming falsely that the oral vaccine leaves Pakistani children sterile. Last year, a Taliban commander in northwest Pakistan announced a ban on polio vaccines for children in the region as long as the United States continued its campaign of drone strikes. At least 16 cases of polio have been reported this year in Khyber Agency. Law and order problems in Bara have left it particularly vulnerable to the disease, which has been declared eradicated from adjacent India. Polio, which can cause permanent paralysis in hours, remains endemic only in Pakistan, Nigeria and Afghanistan. After its case count spiked sharply last year, Pakistan stepped up eradication efforts. The numbers fell from 198 in 2011 to 58 in 2012, but that progress has stopped: Pakistan is the only one of the three countries where polio is endemic to see its numbers go up this year, according to Dr. Bruce Aylward, the World Health Organization's assistant director-general for polio, emergencies and country collaboration. As of November 19, it has seen 63 cases this year versus 54 cases as of that date last year, he said last week in a telephone interview. A second concern is spread of the infectious viral disease from Pakistan to other parts of the world -- cases diagnosed this year in Afghanistan have been linked directly to virus from Pakistan, he said. Vaccination campaign against polio, other diseases begins in Mideast . Journalist Zahir Shah Sherazi reported from Peshawar, CNN's Shaista Aziz and Saima Mohsin wrote from Islamabad, and CNN's Tom Watkins contributed from Atlanta .
The teachers had supported a polio vaccination campaign at their school .
A phony polio campaign set up by U.S. intelligence has fomented opposition to such work .
Since July 2012, at least 22 polio workers have been killed .
Peshawar, Pakistan (CNN) -- Seven teachers abducted last week for supporting a polio vaccination campaign in Pakistan's tribal Khyber Agency have been released by militants, their school principal said Tuesday. "All the teachers have been released after they were questioned over their activities by militant group Lashkar-e-Islam," Hira Public School Principal Qasim Khan told CNN. The principal would not say what information the militant group wanted from the teachers, who were abducted Thursday. The militant group, which has connections to the Pakistan Taliban, opposes polio vaccinations, accusing polio workers of pursuing a political agenda. Anti-polio campaigns have been targeted by militants in Pakistan since U.S. intelligence officials used a fake vaccination program to help in their hunt for Osama bin Laden in 2011. Under cover of the program, the CIA sought to collect DNA samples from relatives of the al Qaeda leader to verify his presence in a compound in Abbottabad. Since July 2012, at least 22 polio workers have been killed. The polio campaign has a history of controversy in Pakistan. Some mullahs have preached against it, claiming falsely that the oral vaccine leaves Pakistani children sterile. Last year, a Taliban commander in northwest Pakistan announced a ban on polio vaccines for children in the region as long as the United States continued its campaign of drone strikes. At least 16 cases of polio have been reported this year in Khyber Agency. Law and order problems in Bara have left it particularly vulnerable to the disease, which has been declared eradicated from adjacent India. Polio, which can cause permanent paralysis in hours, remains endemic only in Pakistan, Nigeria and Afghanistan. After its case count spiked sharply last year, Pakistan stepped up eradication efforts. The numbers fell from 198 in 2011 to 58 in 2012, but that progress has stopped: Pakistan is the only one of the three countries where polio is endemic to see its numbers go up this year, according to Dr. Bruce Aylward, the World Health Organization's assistant director-general for polio, emergencies and country collaboration. As of November 19, it has seen 63 cases this year versus 54 cases as of that date last year, he said last week in a telephone interview. A second concern is spread of the infectious viral disease from Pakistan to other parts of the world -- cases diagnosed this year in Afghanistan have been linked directly to virus from Pakistan, he said. Vaccination campaign against polio, other diseases begins in Mideast . Journalist Zahir Shah Sherazi reported from Peshawar, CNN's Shaista Aziz and Saima Mohsin wrote from Islamabad, and CNN's Tom Watkins contributed from Atlanta .
by militants in Pakistan since U.S. intelligence Abbottabad. Since July 2012, at least 22 polio workers have been killed. The polio campaign has