Salt Lake International Airport, Utah military installations and the State Capitol have tightened security to their highest levels in recent memory.

Before shots were fired in the Persian Gulf, security at the airport was at level two, but by 10 p.m. the Federal Aviation Administration requested an increase to level four - the highest defined level.Airport director Louis E. Miller said most of the precautions taken at level four are classified and cannot be disclosed. But travelers will notice:

- Canine teams watching for and inspecting unattended packages.

- Additional security guards at terminals and in the concourses.

- No unattended cars allowed within 100 feet of the terminal.

- Only passengers with tickets will be allowed in concourses.

"Passengers are being very understanding and cooperative," Miller said Thursday.

Miller, who has been airport director for eight years, reportedly said this is highest level of security requested at Salt Lake International that he can remember.

Security measures were also stepped up at military installations around the state, although military policy prohibits detailed descriptions of any changes.

Security checks at the Hill Air Force Base gates created long lines of cars and trucks waiting to get onto the facility, but only one minor traffic accident was reported, according to police agencies in surrounding cities.

Security guards checked vehicles and in some cases personal identifications of all traffic into and off the base, police said. Workers reported sitting in line for up to 1 1/2 hours to get onto the base.

Trucks entering the base through the truck gate on Hill Field Road west of the main gate were being searched thoroughly, and the line of trucks waiting to get onto the base stretched for several miles east, all the way to US 89, police reported.

At Tooele Army Depot, standard security procedures are being "strictly adhered to," a spokeswoman said.

Maj. Gen. John L. Matthews, Utah adjutant general, said visitors at the Utah National Guard headquarters in Draper must go through a more involved screening before being allowed inside the building.

The civilian secretary controlling access to the front doors has been replaced by a member of the military staff. Signs indicating Guard staff is operating under threat level "Bravo" are scattered around the halls inside.

The state Capitol, where the Legislature is in session, is the only state government facility with increased security, Utah Public Safety Commissioner Doug Bodrero said.

Additional guards are accompanying the Governor and Utah Highway Patrol Troopers have been stationed at all entrances to visually screen people coming into the building.

Lawmakers have also been informed of security procedures and evacuation plans in case anything does happen. But nothing has.

"There is no indication of terrorist activity. We are just looking for those sympathetic to the Iraqi cause and for (unscheduled) anti-war protests," Bodrero said.

No protests had been scheduled for Thursday. But Bodrero said any groups wanting to demonstrate will be carefully screened and evaluated.

North Salt Lake oil refineries also have taken steps.

"We have additional security measures taking place," said Randall Couch, Salt Lake manager for Amoco, which has a pipeline from Fort Laramie, Wyo., to Salt Lake City.

"It's in everybody's best interest to keep the refinery secure. It's a safe place, but it's a hazardous place too," said Chevron refinery manager Lance Gyorfi.

US WEST Communications spokesman Gary Spendlove said, "Under normal security, it would be very difficult to damage the phone system. But we are strengthening measures (placing guards) at key buildings with switching systems and customer records."

Other steps the phone company was taking include checking packages brought into buildings and advising employees to wear their name identification tags.

Water districts have asked employees to watch for unusual activity near treatment plants and to take extra care in locking gates and doors.

Managers said water is tested daily for contamination, although the plants are limited in what they can detect.

"We are kind of edgy here," said Salt Lake County Water Conservancy District manager David Ovard.

Deseret News staff writers Don Rosebrock, Marjorie Cortez and Lisa Riley-Roche contributed to this story.