Pakistani officials say five American men recently arrested in Pakistan had planned to attack sites in that country, including possibly a nuclear plant.
The officials told media the five young Muslim men had established contact with Taliban militants and had planned to travel to the tribal region in northwest Pakistan.
They say the Chashma nuclear power plant in Punjab province may have been one of their targets.
The five men, all from the Washington, DC area, were arrested earlier this month in Sargodha in Punjab province at the home of a leader of the banned militant group Jaish-e-Mohammad (Army of the Prophet Mohammad). The Pakistan-based group has ties to al-Qaida.
Police say the men used Internet sites to try to contact militants in Pakistan before traveling there from the U.S. in late November.
Pakistani investigators are interrogating the five Americans. U.S. FBI agents in Pakistan have also questioned them.
The Council on American Islamic Relations, a U.S. civil rights group representing Muslims, said the men made a "farewell video" with the message that Muslims must be defended.
Some information for this report was provided by AP and Reuters.