A man has been arrested in the United States over an alleged plot to attack train stations in the Washington DC area.
Farooque Ahmed, 34, of Ashburn, Virginia was conspiring with people he believed were from al-Qaeda, the US Department of Justice said.
Mr Ahmed, a naturalized US who was born in Pakistan, was taken into custody on Wednesday morning. If convicted he faces up to 50 years in prison.
He is alleged to have conducted surveillance of a metro station in Arlington, on the outskirts of Washington, DC, on four occasions. and to have offered suggestions about where to place explosives to kill people in simultaneous attacks planned for 2011.
The charges accuse him of telling an person he believed to be affiliated with al Qaeda that between 4pm and 5pm would be the best time for an attack to cause the most casualties.
Officials said that the public was never in any danger during the investigation and that federal authorities had closely monitored Ahmed's activities until his arrest.
Mr Ahmed's arrest is the latest in a line of investigations of US citizens or residents for involvement in alleged domestic terror plots. Last year there were arrests over plans for attacks in Texas, Colorado and Illinois, the BBC reports.
More recently Faisal Shahzad was convicted of attempting to bomb Times Square in New York.