Yesterday's subway and bus bombings in London prompted officials to send bomb-sniffing dogs into the downtown Seattle Metro bus tunnel and increase the police presence at other key transportation sites, even as officials acknowledged there was no hint of a threat here.

Additional patrols were assigned at Amtrak's King Street Station and elsewhere in the Metro transit system. The Coast Guard late yesterday also ordered increased security screenings for most of the state's passenger ferries, requiring additional inspections of vehicles and mandatory screening of all large trucks and vans.

However, the Department of Homeland Security's decision to raise the national threat level from yellow/elevated to orange/high extended only to mass-transportation systems.

Mike Milne, a spokesman for U.S. Customs and Border Protection, said no additional security measures were being taken along the U.S.-Canada border, although agents were "operating under heightened awareness."

By evening, the Regional Communication and Emergency Coordination Center in Renton — opened yesterday morning after the first news of the attacks — was being buttoned up again, said Eric Holdeman, director of the King County Office of Emergency Management.

Holdeman participated in a national conference call yesterday afternoon with other state and major metropolitan emergency officials. The security measures were initiated "out of an abundance of caution," and Holdeman said they will remain in place indefinitely.

"The Joint Terrorism Task Force is really ramped up and is looking under every rock," he said.

Mayor Greg Nickels said that while there was no specific threat to Seattle, he had instructed city police and firefighters to increase security efforts. Likewise, King County Sheriff Sue Rahr said she ordered additional security hours before the threat level was increased.

"The message to the public is that we're prepared, we're working together and we have safeguards in place," the sheriff said. "I don't think people know how much planning and training and preparedness has already taken place.

"We have to reassure the public the transit system is safe because if people shy away from the transit system, the terrorists win — and we lose all those extra sets of eyes and ears."

Earlier, Rahr joined King County Executive Ron Sims and Seattle police Assistant Chief Nick Metz for the first live news conference to be broadcast from the Regional Communication and Emergency Coordination Center.

"There will be increased police patrols in the downtown transit tunnel and elsewhere in our system," Sims said.

Metro bus drivers, who are required to inspect their vehicles before leaving the bus yard, were urged to be extra vigilant and passengers are asked to call 911 if they see anything suspicious, Sims said. "We have done everything humanly possible to make sure people can use our buses and other modes of transportation," he said. "With a terrorist attack, they want you to live in fear. ... I want people to be alert but not fearful."

According to Metz, Seattle Police Chief Gil Kerlikowske called a meeting with Seattle fire officials for this morning to decide on a course of action within the city.

Officials declined to detail the measures being taken to protect the public-transit system but said local responders have practiced what to do in the event of a bombing.

In March, a regional drill was conducted with 400 people from more than 40 local, state and federal agencies. The exercise — dubbed "Double Trouble" — was a simulated attack on two modes of public transportation, Holdeman said.

Mike DeCapula, the homeland-security program manager for King County Metro Transit, said the county has spent more than $1 million in federal Homeland Security grant money to "harden" the bus tunnel, develop a regional critical-transportation plan and pay for a mobile command-and-control center.

The county recently received $900,000 more and will split an additional $1.1 million in security money with other regional transportation agencies, he said.

Sound Transit spokesman Lee Somerstein said riders of the agency's trains, buses and Tacoma light-rail line would likely see more security officers riding the system and at stations.

Like Metro, Sound Transit asked passengers and operators to report suspicious activity or unattended objects — no matter how trivial — to drivers or security personnel.

"One of our best security measures is our passengers and our operators. We ask them to be extra alert now," Somerstein said.

But, he added, "I can't emphasize enough that people should go about their daily lives."

Seattle Times staff reporters Maureen O'Hagan, Nick Martin, Brian Alexander and Victor Gonzalez contributed to this report.

Mike Carter: 206-474-3706 or mcarter@seattletimes.com. Sara Jean Green: 206-515-5654 or sgreen@seattletimes.com