The young Muslim men, who are from the Washington, D.C., area, were picked up in Pakistan earlier this month in a case that has spurred fears that Westerners are traveling to the South Asian country to join militant groups.
Pakistani police and government officials have made a series of escalating and, at times, seemingly contradictory, while U.S. officials have been far more cautious, though they, too, are looking at charging the men.
A Pakistani government official alleged Saturday that the men had established contact with Taliban commanders and planned to attack sites in Pakistan. Earlier, however, 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 also had exchanged e-mails 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.
Any nuclear activity in Pakistan tends to come under scrutiny because of the South Asian nation's past history of leaking sensitive nuclear secrets due to the actions of the main architect of its atomic weapons program, Abdul Qadeer Khan. But as militancy has spread in Pakistan, officials have repeatedly insisted the nuclear weapons program is safe.
Pakistani police plan to recommend that courts charge the five men with collecting and attempting to collect material to carry out terrorist activities in Pakistan, police official Nazir Ahmad told The Associated Press. The punishments for those charges range from seven years to life in prison, he said.
Officials in both countries have said they expected the men would eventually be deported back to the United States, but charging the men in Pakistan could delay that process. Pakistan's legal system can be slow and opaque.
In an interview with The Associated Press on Saturday, Punjab province Law Minister Rana Sanaullah said the men had established contact with Taliban commanders. He said they had planned to meet Pakistani Taliban chief Hakimullah Mehsud and his deputy Qari Hussain in Pakistan's tribal regions before going on to attack sites inside Pakistan.
The nuclear power plant "might have been" one of the targets, Sanaullah alleged.
The FBI, whose agents have been granted some access to the men, is looking into what potential charges they could face in the U.S. Possibilities include conspiracy to provide material support to a terrorist group.
The U.S. Embassy has declined to comment on the potential charges and would not say what efforts Washington was making to bring the men back. The five were arrested in Sargodha earlier this month, but are being held in Lahore, the capital of Punjab province.
In Islamabad, it was a political bombshell that dominated the news this week, reports CBS News correspondent Terry McCarthy. A Supreme Court decision has left over 150 politicians - including four cabinet ministers - open to investigation on corruption charges.
Defense Minister Ahmed Mukhtar is on the list. He says he is innocent. He was meant to go on an official visit to China last week, but was prevented from leaving the country.
The political crisis comes at the worst possible time for the United States, which needs Pakistan's help now more than ever as it pours more troops into neighboring Afghanistan.