WASHINGTON — Braced for protests by 99 groups and a new "global terrorist environment," security officials plan to protect the inauguration of President-elect Donald Trump with buses, dump trucks and heavy vehicles loaded with cement to thwart anyone who might try to plow vehicles through the crowds.

"We know of no specific credible threat directed toward the inauguration, Homeland Security Secretary Jeh Johnson said Friday. But he said that lack of a threat "is only part of the story."

With memories fresh of vehicle attacks in France and Germany, the Secret Service will lead a security force of 28,000 to protect a crowd that could reach 900,000 on Inauguration Day, Johnson said.

Perhaps most visible will be large vehicles that will be used to seal the perimeter of the National Mall, which Johnson described as "more fortified" than usual.

"That is a precaution that we are doubling down on in particular this inauguration," Johnson said.

The security force will include 10,000 personnel from the Department of Homeland Security, which oversees the Secret Service, and other federal agencies, including the FBI, U.S. Park Police, U.S. Capitol Police, the Transportation Security Administration, the Federal Emergency Management Administration and the Federal Protective Service.

More than 3,200 police officers from across the country have volunteered to help.

And 44 states, along with the District of Columbia, will deploy more than 7,500 National Guard soldiers and airmen to help with security.

© REUTERS/Mark Kauzlarich FILE: Pedestrians pass dump trucks filled with sand set up as New York Police Department barricades near New Year's Eve festivities in the Times Square area of New York, December 31, 2016. That includes 20 members of the Washington state National Guard's 10th Civil Support Team, who will conduct radiation sweeps to make sure no one sneaks in a dirty bomb. They've made similar searches for any signs of radioactive material during the pope's U.S. visit in 2015 and last year's Super Bowl in San Francisco.

"If you can get a radiation source through there and actually create some kind of explosion, you could do a lot of damage," said First Sgt. Paul Gautreaux, 48, of Olympia, Wash. "But our equipment is going to pick it up."

Florida is sending 341 Guard members, including a team that will provide religious support. Missouri, Georgia, Kansas, Kentucky and Mississippi are sending mobile kitchens and military cooks. And South Carolina has lined up 30 to help with crowd control.

"I've never been involved in an inauguration _ it's a pretty big honor," said Capt. Michael Meissner, 34, the officer in charge of the South Carolina group and the mayor of Pacolet, a town of 2,200 in South Carolina's Spartanburg County. "We all will be trained, so we should be able to deal with anything that comes our way. The big thing is you've got to be positive."

Security will be especially tight after one of the most bitterly-fought elections in history and a possible weekend crowd that could exceed 1 million for the inauguration and protests, including the Women's March on Washington on Jan. 21 that promises to dwarf attendance at the inauguration itself.

"While we're prepared for any rise in tensions, we're entering the inauguration with the mindset that this will be another peaceful transfer of power," said D.C. National Guard Maj. Michael Odle.

Odle said Guard members will be deputized as special members of the Washington, D.C., police force Thursday at a ceremony at FedEx Field in Landover, Md.

Overall, roughly 90 Guard members will be assigned to radiation sweeps. While the Washington state team has long been recognized for its expertise, mainly because of its work at the Hanford Nuclear Reservation, it will be helped by similar units from Texas, North Dakota and the Virgin Islands.

Washington, D.C., and Pennsylvania will provide the most Guard members, nearly 2,000 and 1,562, respectively.

Odle said a few states aren't participating because the Guard issued a request for help and filled the 7,500 slots first come, first served.

"Once we hit our cap, we don't need any more support or assistance," he said.

While freezing weather has complicated previous inaugurations, the early forecast for Trump's big day calls for temperatures in the 50s.

That would mean fewer headaches for First Lt. Taylor Wagner of Tallahassee, operations officer for the Florida unit, who will keep track of shift changes and the rotation of personnel assigned to manage the crowd.

"We don't want them out there too long in the cold," he said. "But most of our job is just keeping the crowd moving in the right direction and try not to get trampled. We're very proud to be serving the citizens of the United States."

Guard members say they'll be ready for anything.

"Can someone slip through the cracks? Sure I'm a little concerned, but I don't lose any sleep over it at nighttime," Gautreaux said. "There's always that little bit of fear there: What could happen. Could things go wrong? But I'm confident."

Thomas said his biggest worry is that protesters "might get out of control."

"There's the risk of terrorists, but my primary concern would be for protesters," he said. "There's a lot of stuff going on, a lot of moving parts, but the team that we have here is highly trained and we have full confidence that we'll be able to handle anything that comes our way."

Friday, Homeland Security chief Johnson said federal officials used social media and permit applications to identify 99 groups —"some pro, and some con" — that are expected to protest over three days; 63 of those protests are planned for Inauguration Day.

The inaugural festivities are to begin Thursday with a wreath-laying ceremony at Arlington National Ceremony and a "welcome concert" at the Lincoln Memorial, and they'll conclude Saturday with a national prayer service at the Washington National Cathedral.

Johnson, speaking at the multiagency command center in suburban Virginia that will be the communications hub for all security forces, said that security planners must be concerned both with protesters and the possibility of "violent extremism."

"The global terrorist environment is very different ... even from 2013," he said, referring to the second inauguration of outgoing President Barack Obama.

Johnson declined to estimate the total cost of security but said, "I'm sure it's a huge number."



