TERROR IN OKLAHOMA CITY : Many Children Absent at O.C. Federal Building Care Center : Reaction: Extra security measures are taken because of deaths at a similar Oklahoma City facility. Tensions are felt throughout the county.

Dozens of toddlers were absent from a day-care center at a Laguna Niguel federal building Thursday, one day after the Oklahoma City bombing that killed youngsters at a similar facility.

Day-care employees said that about a quarter of the 178 children in their charge stayed away from the Ziggurat Child Development Center, a day-care facility at the Chet Holifield federal building.

A guard stood at the door, questioning visitors and asking for identification, and a parking lot next to the center’s playground was off-limits to motorists, said Shauna Boger, the center’s director.

“Most of the parents didn’t have their children watching television, so the children are pretty calm,” Boger said. “It’s me who’s the nervous one.”

Tensions simmered among federal workers throughout the county, and officials prepared to further tighten security, although no unusual incidents were reported.

As federal agents issued arrest warrants for two men, the California Highway Patrol in Santa Ana issued a radio alert to officers to watch for a Volkswagen hatchback that might contain suspects related to the Oklahoma City bombing.

The scanner broadcast, which came about 11 a.m. on request by the U.S. Customs Service, said the hatchback might be heading south from Los Angeles on Interstate 5 toward the U.S.-Mexican border.

The alert matched the vehicle description issued by U.S. Customs on Wednesday afternoon to local law enforcement agencies, according to Tustin Police Sgt. Jeff Beeler. The message warned that a Volkswagen hatchback with suspects possibly linked to the Oklahoma City disaster could be heading south, and said that FBI agents were dispatched to San Ysidro.

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U.S. Customs spokesman Greg Doss in Los Angeles confirmed that the Volkswagen alert came from his agency, but said, “To our knowledge, it’s not related to the Oklahoma bombing.

“We have a lookout for a vehicle. We just want to interview the driver and any passengers,” said Doss, who declined to elaborate, saying the matter was “under investigation.”

Officials on Thursday raised a security alert for federal buildings to a “moderate” level until further notice. Two bomb threats had been received a day earlier, at the Santa Ana FBI office and Anaheim City Hall.

Charlie Almanza, assistant chief deputy U.S. marshal in Santa Ana, said Thursday that local offices were preparing to implement the heightened security measures. The heightened alert means workers will be asked to display government identification to get into buildings; visitors and commercial personnel will need to show a state driver’s license or comparable photo ID, and officials will inspect packages, handbags and other containers carried by visitors.

Although everyone was more “security conscious,” Almanza said, Thursday was “very quiet and calm.”

“Everything was business as usual,” he said.

But that did not allay the fears of parents who use the Ziggurat day-care center.

Debby Howell, a Laguna Niguel attorney, said she will continue to take her 8-month-old son, Peter, to the day-care center because “the care givers are great and he loves it there.”

“But that doesn’t mean I’ll feel good about it,” Howell said. “There’s always going to be that security issue. From now on, I’m going to have to worry about more than just injuries and illnesses.”

In the offices of the Immigration and Naturalization Service above the day-care center, employees went about their business with a heightened awareness.

“There a lot of people who aren’t entirely happy with what we do. We share a building with the IRS and a lot of people aren’t happy with what they do,” INS spokesman Ron Rogers said. “People now are aware that, ‘Hey, we could be a target.’ ”

Rogers said the office has had its share of bomb threats, but normally workers file out of the building with little commotion. But Thursday, a false fire alarm in the building sent a wave of tension through the ranks.

“People just got really nervous. Someone got on the intercom right away and said do not evacuate the building,” Rogers said. “I have not seen this kind of awareness and concern. I think people feel it’s really close.”

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Elsewhere in Orange County, residents tied up phone lines of some social service groups to ask what they could do to help.

At the Salvation Army headquarters in Tustin, about 20 people called Thursday wanting to do their part in assisting those whose lives were devastated by the blast.

“Right now, we’re working with the division commander in the Arkansas/Oklahoma region to find out exactly what kind of assistance is needed,” said Warren Johnson, assistant coordinator for the Salvation Army in Orange County. “While we’re doing that, we’re taking money donations.”

The organization asks that donations be sent to Salvation Army Oklahoma City Disaster, 1020 Pioneer Road, Tustin, CA 92680. Information: (714) 832-7100.

On Monday, the Jewish Federation of Orange County will meet to discuss a plan for relief efforts to Oklahoma City, Marketing Director Debbie Stein said.

The nonprofit organization was among many charitable groups that helped victims of the Laguna Beach fire in October, 1993. During that disaster, the group set up a fund for donations and distributed non-perishable food items, clothes, blankets and hardware to victims.

“We know that we are going to do something for the people in Oklahoma (City),” Stein said. “But we don’t know what, specifically, at this point.”

Times staff writer Anna Cekola contributed to this report.