WASHINGTON, Aug. 12 (Xinhuanet) -- US Department of Homeland Security announced Friday that it will lower the terrorism threat level after evening rush hour Friday for mass transit systems, which had been placed under extra security since the July 7 bombing attacks in London.

    The color-coded threat level will be lowered from orange, or high risk, to yellow, or elevated risk, at 8 pm local time for transit systems, according to a statement issued by Homeland Security Secretary Michael Chertoff.

    "There is no specific, credible intelligence information indicating that an attack in the United States is imminent, " he said in the statement.

    However, because bombings targeting transit systems in London and Madrid "were conducted without warning," Chertoff said, extra vigilance is still warranted by commuters and travelers.

    "Although the overall national threat level is being lowered for mass transit systems, many transit systems, particularly the larger systems, will maintain a strengthened baseline level of preparedness beyond what existed before the London attacks," he said.

    The orange level means more heavily armed police, often with bomb-sniffing dogs, patrolling subway stations and platforms.

    It also means more video surveillance of transit points, frequent inspections of trash receptacles and random searches of passenger bags. Enditem