Chief Kevin Cartwright, a fire department spokesman, said that one employee who was on the ninth floor, where the explosion occurred, suffered burns to his hands and was taken by ambulance to Johns Hopkins Bayview Medical Center.

The spokesman said that a woman who had been reported missing has been found; he said she was among the people safely evacuated and was not injured.

The cause of the explosion, which shook nearby homes, has not been determined. City building inspectors and structural engineers were inside the nine-story sugar refinery plant to investigate the extent of the damage and determine whether the building can reopen and work resume.

"We're very, very fortunate this wasn't any worse than it was," Cartwright said.

Brian O'Malley, president and chief executive of parent Domino Foods Inc. in Iselin, N.J., said that as of early afternoon the company had little information on the explosion's effects on the structure of the building or manufacturing operations.

"We haven't had any formal update as to what the prognosis is," he said. "We know it was a fairly serious explosion, so it's probably going to take a little time."

O'Malley expressed relief that all of the employees had been accounted for and that there were no fatalities.

The explosion occurred about 10 a.m. and nearly 100 firefighters, including those on fireboats, were at the scene. Cartwright said fires were reported on the sixth floor. The fire department struck three alarms, bringing 35 vehicles to the scene.

Firefighters had the blaze under control at 11:37 a.m. and reported that an extensive overhaul would to be completed. A damage estimate was not available.

Around 11:30 a.m., smoke was still pouring out of the windows that had been blown out of the top floors of the building -- a landmark in Baltimore with its large neon sign -- but flames were not visible. Fire officials have set up a command center at a Royal Farms convenience store on Key Highway.

"I've never seen anything like this happen," said Jay Peters, who works for Domino and pulled up for his shift this morning to discover the fire. "First and foremost, we are worried about injuries. And then we're worried about whether we will have a job in the future."

Employees who emerged from the building were reassuring relatives that they're OK. Residents living nearby said they felt the ground shake when the explosion occurred.

Gina Orsino, a young mother who lives in the 1400 block of Woodall Street across from the plant, was on the phone with her husband when she felt the explosion.

"I was feeding the baby and I thought the ceiling was caving in," she said. "I looked outside and saw all the firetrucks and helicopters. . . . I opened the door and it was like 'Oh, my God!"

Her husband, Orlando Orsino, rushed home from the restaurant he owns a few blocks away. He said the couple's baby, 11-month-old Luca, started crying after the blast. But an hour later, safe in his father's arms, Luca was smiling and seeming to enjoy the activity.

While many neighbors expressed no qualms about living near the familiar Locust Point landmark, Gina Orsino said she has had her worries.

"It was like an accident waiting to happen," she said.

The Domino plant opened in 1922. Ground was broken May 17, 1920, for the Locust Point sugar refinery, which was constructed alongside the Patapsco River and the rail tracks of the old Baltimore and Ohio Railroad.