OKLAHOMA CITY (AP) _ A car bomb ripped a nine-story hole in a downtown federal office building today, killing at least eight people, including six children, and injuring at least 200. Other victims were trapped in the wreckage.

Mayor Ron Norick called it a car bomb, and said it left a crater 8 feet deep.

The explosion, similar to the terrorist car bombing that rocked New York's World Trade Center two years ago, happened just after 9 a.m., when most of the more than 500 federal workers were in their offices. The death toll surpassed the trade center attack.

Mike Osburn, deputy chief of staff for Gov. Frank Keating, said the Oklahoma Civil Emergency Management Agency confirmed eight dead included six children.

The explosion at the Alfred Murrah Building, which occurred shortly after 9 a.m., could be felt 30 miles away. Black smoke streamed across the skyline, and glass, bricks and other debris were spread over a wide area.

The building, which has a day-care center as well as a variety of federal offices. Some children were injured at another day car center nearby.

U.S. Rep. Ernest Istook said six Secret Service agents were unaccounted for.

The bomb was perhaps 1,000 to 1,200 pounds, said John Magaw, director of the federal Bureau Alcohol, Tobacco and Firearms. As for whether his agency suspected terrorists, Magaw told CNN: ``I think any time you have this kind of damage, this kind of explosion, you have to look there first.'' Police at one point said a second, unexploded bomb was found, but Magaw said no other bomb was confirmed.

As of early afternoon, no one had claimed responsibility for the blast.

After the explosion, emergency crews set up a first aid center nearby, and some of the injured sat on the sidewalks, bloodied on their heads or arms, awaiting aid. St. Anthony Hospital put out a call for more medical help, and at midday, officials at that hospital posted a list of more than 200 names of injured so worried relatives could look for loved ones.

President Clinton directed that emergency federal assistance be offered to local authorities.

Carole Lawton, 62, a secretary in the department of Housing and Urban Development, said she was sitting at her desk on the seventh floor when ``all of a sudden the windows blew in. It got real dark and the ceiling just started coming down.'' She then heard ``the roar of the whole building crumbling.''

She managed to crawl down some stairs and was not injured.

Another worker who would not give his name told KFOR-TV: ``I came out from under the desk and there just wasn't any building left around me. Our whole office area is gone.''

More than two hours after the explosion, people were still trapped in the building.

``We have to crawl on our stomachs and feel our way and we're talking to victims who are in there and reassuring them that we're doing everything within the good Lord's power to reach them and get to them,'' Assistant Fire Chief Jon Hansen said.

``It's going to be a very slow process.''

Besides the local offices of the bureau of Alcohol, Tobacco and Firearms, the building houses such agencies as Social Security, Veterans Affairs, the Drug Enforcement Administration, Housing and Urban Development, a federal employee credit union, a daycare center and military recruiting offices.

In all, more than 500 federal employees assigned to building, said Anne Marshall, a spokeswoman for the General Services Administration.

The explosion occurred on the second anniversary of the fiery, fatal ending of the federal siege of the Branch Davidian compound in Waco, Texas. That siege began with a raid by ATF agents on Feb. 28, 1993.

Oklahoma City FBI spokesman Dan Vogel said he wouldn't speculate if there was a connection. The FBI is not housed in the building downtown but is in an office complex about five miles away. Dick DeGurin, who represented Davidian leader David Koresh, said any such link was just speculation.

At the scene, the nine-story building looked like it had been rocked by a bomb. From top to bottom, floors caved in. The north side of the building was gone. Burning debris and burning cars lined streets.

People frantically searched for loved ones, including parents whose children were in a daycare center housed in the building. Downtown business stopped as other nearby buildings were evacuated.

``I thought we were dead,'' said Ginny Grilley, office manager for Trammel Crow Co. She was on the 30th floor of City Place, which is several blocks away. ``I've never heard anything that loud.''

She said she could see ``a lot of damage all over'' to nearby buildings.

``It was just terrifying,'' she said. ``When you look up and see most of that building gone and cars destroyed and people hurt ... it was just terrible.''

The FBI was setting up a command center at its Washington headquarters to manage the investigation.

The building is located at 200 N.W. Fifth St.

Six people died and 1,000 were injured in the World Trade Center bombing in February 1993. A rented van blew up in a parking garage beneath one of the center's twin towers. Four men have been convicted in the blast.