Police in Pakistan are trying to determine whether five arrested Americans planned to attack a complex that houses nuclear power facilities.
The young Muslim men from the Washington DC area were picked up in Pakistan earlier this month in a case that has spurred fears that Westerners are travelling there to join militant groups.
Pakistani police and government officials have made a series of escalating and, at times, seemingly contradictory allegations about the men's intentions, while US officials have been far more cautious, though they, too, are looking at charging the men.
A Pakistani government official said that the men had established contact with Taliban commanders and planned to attack sites in Pakistan.
Earlier, local police accused the men of intending to fight in Afghanistan after meeting militant leaders.
The men had a map of Chashma Barrage, a complex that along with nuclear power facilities houses a water reservoir and other structures, said Javed Islam, a senior police official in the Sargodha area of Punjab province.
He stressed the men were not carrying a specific map of any nuclear power plant, but rather the whole of Chashma Barrage.
The detained men had also exchanged emails about the area, Islam said.
"We are also working to retrieve some of the deleted material in their computers," he said.
Pakistan has a nuclear weapons arsenal, but it also has nuclear power plants for civilian purposes.