Police are trying to determine whether five Americans detained in Pakistan had planned to attack a complex that houses nuclear power facilities.

The young Muslim men, who are from the Washington DC area, were arrested in Pakistan earlier this month. Pakistani police and government officials have made a series of escalating and, at times, seemingly contradictory claims about the men's intentions. US officials have been far more cautious, but they, too, are looking at charging the men.

A Pakistani government official alleged on Saturday that the men had established contact with Taliban commanders and had planned to attack sites in Pakistan. Earlier, however, local police accused the five of intending to fight in Afghanistan after meeting militant leaders.

The men allegedly 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 where the men were arrested.

He stressed that they were not carrying a specific map of a nuclear power plant, but a map of the whole Chashma Barrage. The detained men had also exchanged emails about the area, Islam claimed. "We are also working to retrieve the deleted material in their computers," he said.

Pakistan has an arsenal of nuclear weapons, but also has nuclear power plants for civilian purposes.

Any nuclear activity in Pakistan tends to come under US scrutiny after the main architect of its atomic weapons programme, Abdul Qadeer Khan, was accused of leaking sensitive nuclear secrets. But, as militancy has spread in Pakistan, officials have repeatedly insisted that the nuclear weapons programme is secure.

A Pakistani police official, Nazir Ahmad, told the Associated Press that the force would ask the courts to charge the five men with collecting and attempting to collect material to carry out terrorist activities in the country. If convicted, the charges carry a sentence of from seven years to life in prison, he said.

Officials in Pakistan and America say they expect the suspects eventually to be deported back to the US, but charging the men in Pakistan could delay that process. The country's legal system can be slow and opaque.

In an interview with the Associated Press on Saturday, Punjab province's law minister, Rana Sanaullah, claimed the men had established contact with Taliban commanders. He said they planned to meet the Pakistani Taliban chief, Hakimullah Mehsud, and his deputy, Qari Hussain, in the tribal region before going on to attack sites inside Pakistan. The nuclear power plant "might have been" one of the targets, Sanaullah alleged.

FBI agents have been granted some access to the men, who are being held in Lahore, capital of Punjab province, and are looking into what potential charges they could face in the US. Possibilities include conspiracy to provide material support to a terrorist group.

The five were arrested in Sargodha earlier this month, but are being held in Lahore, the capital of Punjab province.