OKLAHOMA CITY (AP) _ A car bomb ripped deep into America's heartland Wednesday, killing at least 27 people and leaving 300 missing in a blast that gouged a nine-story hole in a federal office building.

The dead included at least 12 youngsters, some of whom had just been dropped off by their parents at a day-care center.

There was no immediate claim of responsibility for the attack, the deadliest U.S. bombing in 75 years.

At least 200 people were injured _ 58 critically, according to Fire Chief Gary Marrs _ and scores were feared trapped in the rubble of the Alfred P. Murrah Federal Building more than nine hours after the bombing.

Two people were pulled from the rubble Wednesday night but died a short time later, said Assistant Fire Chief Jon Hansen. Hansen said a woman was trapped in the basement, who said there were two others down there. She didn't know if they were dead or alive.

The death toll was certain to rise.

``Our firefighters are having to crawl over corpses in areas to get to people that are still alive,'' Hansen said.

Attorney General Janet Reno refused to comment on who might have been behind the attack. President Clinton called the bombers ``evil cowards,'' and Reno said the government would seek the death penalty against them.

A police source, who requested anonymity, said FBI agents were trying to piece together a van or a truck that was believed to have carried the explosives. An axle of the vehicle was found about two blocks from the scene, the source said.

Their clothes torn off, victims covered in glass and plaster emerged bloodied and crying from the building, which looked as if a giant bite had been taken out of it, exposing its floors like a dollhouse.

Cables and other debris dangled from the floors like tangled streamers in a scene that brought to mind the car bombings at the U.S. Embassy and Marine barracks in Beirut in 1983.

``I dove under that table,'' said Brian Espe, a state veterinarian who was giving a slide presentation on the fifth floor. ``When I came out, I could see daylight if I looked north and daylight if I looked west.''

Mayor Ron Norick said the blast, which left a crater 30 feet long and 8 feet deep, was caused by a car bomb. He said the car had been outside, in front of the building.

``Obviously, no amateur did this,'' Gov. Frank Keating said. ``Whoever did this was an animal.''

Police Sgt. Bill Martin said at least 26 people were killed, 12 of them children.

Earlier in the day, paramedic Heather Taylor said 17 children were dead at the scene, a figure later disputed by police. Dr. Carl Spengler, one of the first doctors at the scene, said the children, all at the day-care center, ranged in age from 1 to 7, and some were burned beyond recognition.

Reno said that 300 people were unaccounted for by late afternoon. About 20 of 40 children in the day-care center were missing.

The explosion, similar to the terrorist car bombing that killed six people and injured 1,000 at New York's World Trade Center in 1993, occurred just after 9 a.m., when most of the more than 500 federal employees were in their offices.

The blast 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 north side of the building was gone. Cars were incinerated on the street.

People frantically searched for loved ones, including parents whose children were in the building's day-care center.

Christopher Wright of the Coast Guard, one of those helping inside the building, said rescuers periodically turned off their chainsaws and prying tools to listen for pleas for help, ``but we didn't hear anything _ just death.''

``You're helpless really, when you see people two feet away, you can't do anything, they're just smashed,'' he said.

``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,'' the Fire Department's Hansen said. ``It's going to be a very slow process.''

The building, which opened in 1977, has offices of such federal agencies as the Bureau of Alcohol, Tobacco and Firearms, Social Security, Veterans Affairs, the Drug Enforcement Administration and Housing and Urban Development, and a federal employee credit union and military recruiting offices.

The bomb was perhaps 1,000 to 1,200 pounds, said John Magaw, ATF director. As for whether his agency suspected terrorists, he told CNN: ``I think any time you have this kind of damage, this kind of explosion, you have to look there first.''

Bob Ricks, agent in charge of the FBI in Oklahoma, said that there were hundreds of leads and that the bureau was treating them all seriously. ``At this point we do not speculate as to who is responsible,'' he said.

The government received calls from six people saying they were from different Muslim sects, asserting they were responsible, a Justice Department official said.

``But there is no way to know if the calls are genuine,'' said this official, who declined to be identified by name. ``They could be hoaxes.''

The governor said he was told by the FBI that authorities were initially looking for three people in a brown pickup truck. Keating said the people were of Middle Eastern descent. The Oklahoma Highway Patrol put out an all-points bulletin for the three. One was described as 25 to 30 and another between the ages of 35 to 38.

The explosion heightened U.S. fears of terrorism. Federal buildings in several cities were evacuated because of bomb threats, and the government ordered tightened security at federal buildings throughout the country.

In 1920, a bomb blast in New York's Wall Street area killed 40 people and injured hundreds. Authorities concluded it was the work of ``anarchists'' and came up with a list of suspects, but all had fled to Russia.

Emergency crews set up a first aid center near the federal building, and some of the injured sat on the sidewalks, blood on their heads or arms, awaiting aid. St. Anthony Hospital put out a call for more medical help, and at midday, posted a list of more than 200 names of injured so worried relatives could look for loved ones.

``It was like Beirut; everything was burning and flattened,'' said Spengler, who arrived minutes after the blast.

Carole Lawton, 62, a HUD secretary, 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.

The explosion occurred on the second anniversary of the fiery, fatal ending to the federal siege of the Branch Davidian compound in Waco, Texas. That siege began with a raid by ATF agents a month and a half earlier.

Oklahoma City FBI spokesman Dan Vogel wouldn't speculate if there was a connection. The FBI's offices are about five miles away. Dick DeGuerin, who was cult leader David Koresh's lawyer, said any such link was just speculation.

In the World Trade Center bombing in February 1993, a rented van blew up in a parking garage beneath the twin towers. Four Muslims were convicted.