Acting on a tip from local residents, Marines today raided an abandoned branch of the Iraqi Atomic Energy Commission south of Baghdad and found several laboratories, gas masks, chemical suits, vats of industrial chemicals and a map listing buildings that contained "radioactive material."

Troops from the 1st Battalion, 7th Marine Regiment, scoured the fortified government complex, but a cursory inspection revealed ordinary levels of radiation and chemical contamination. Commanders said they saw enough to call in a "sensitive site exploitation" team to conduct a more thorough analysis.

"It could be nothing, but the obvious thing to do is clear the place and notify through the chain of command that we have found what may be a sensitive site," said the commander of the 7th Marine Regiment, Col. Steven Hummer, who visited the battalion to inspect the find. "The experts will be able to tell relatively soon."

In the midst of a war launched over allegations that Iraq possesses banned weapons, the Marines kicked in doors and rifled through offices, hoping to uncover what nearly three weeks of war have failed to produce: hard evidence that Iraq has a nuclear, chemical or biological weapons program. On Saturday, Army troops found vials of white powder near the town of Latifiyah in what was called a "chemical facility." Initial tests indicated the substance was not harmful.

It was not clear whether the site raided today had previously been visited by U.N. weapons experts during the several months of inspections that concluded in early March. After the 1991 Persian Gulf War, the U.N. inspectors exposed a covert Iraqi nuclear weapons program, but the latest inspections found no proof that it was re-started.

A convoy of armored vehicles rumbled along a windy, one-lane road to a compound that looked like a rundown college campus, with several office buildings separated by green lawns and palm groves. The facility was bounded on all sides by 100-foot-tall earthen berms. The Marines did not unleash a barrage of artillery to prepare the area, as they have in most previous attacks, because they were concerned that explosions inside the compound could trigger the release of harmful contaminants.

Several hill-like cement bunkers covered in sand guarded the long, winding approach to a series of office buildings. When the Marines arrived, a tank plowed through the iron front gate, and more than 100 Marines streamed through in squads of roughly 14, each assigned to a different section of the compound.

Lt. Andrew Schoenmaker, the nuclear, biological and chemical weapons officer for Bravo company, which led the raid, followed one group of Marines toward a white-brick duplex office building with a gaping hole in the roof that appeared to have been caused by shelling or other weapons fire.

He stopped to search some barrels and then descended into a bunker, scanning its empty rooms with a flashlight, finding only a can of paint. Up ahead, a sergeant used a shotgun to blast open a second-floor entrance, and six Marines burst in, moving from office to office along a narrow corridor. Posters of Iraqi President Saddam Hussein adorned a wall in each room, and the floors were covered by torn oriental carpets.

"Sir, we have a gas mask in here!" shouted Cpl. John Rakestraw, from an office at the end of the hall.

"That's it, I'm going in," said Schoenmaker, climbing the stairs in a few bounding steps and hurrying toward the find. In an adjacent room he found boxes of black latex gloves, and Kleenguard brand coverall suits. He rifled through papers in a glass filing cabinet and found a typed sheet of paper with "heavy water" written in a margin.

He got on the radio: "Don't touch anything," he told the Marines. "Hold in place, we have to get this stuff to higher [headquarters]." He moved on to another building where Marines wearing night-vision goggles found several laboratories containing metal storage drums and large quantities of white powder.

"Good work, gentlemen. That's a good find," said Schoenmaker as he examined a map of the compound -- found in one of the offices -- that listed buildings containing "radioactive material." It was unclear why the map was marked in English. A translator later determined that other buildings were marked for animal testing.

Rooms marked "Wear protective clothing" were left for specialists to search. Cabinets had been placed against some of the laboratory doors, making them harder to open. When one Marine kicked in a door, shattering a container of liquid, U.S. forces were told to leave the building until it could be inspected further for contaminants.

Chief Warrant Officer Carl Hinson, the battalion's nuclear, biological and chemical officer, walked through the complex with a small metal apparatus that could detect radiation and nerve and blister agents in liquid and vapor form. He found nothing out of the ordinary, he said, adding that solids or powders would need to be tested by others.

As the Marines continued their search into the early evening, tanks roamed up and down the streets, while artillery shells rumbled to earth a few miles away. Snipers patrolled the massive berms.

Elsewhere, Marines found more gas masks, magazines for AK-47 assault rifles, Iraqi military uniforms, stacks of Iraqi currency and bags full of Iraqi flags. When Hummer, the regimental commander, arrived at dusk, he was escorted from building to building by a group of officers who explained what had been found in each structure. "I'm certainly not an expert and it's too soon to tell," Hummer told the group, adding that he was not sure when the outcome of any further investigations would be available. "We've done our part."

Lance Cpl. Elios Pelaez, left, of Los Angeles, and Lance Cpl. Stephen Ferris of Walpole, Mass., search a building in Salman Pak, a small town about 15 miles southeast of downtown Baghdad.