A woman who had just been suspended from her job returned to the Kraft Foods baking plant  in Northeast Philadelphia Thursday night and opened fire with a .357 Magnum handgun, killing two co-workers and wounding a third, police said.

The shooter -  identified by coworkers as Yvonne Hiller - was taken into custody by SWAT team members after a standoff on the second floor of the plant at 12000 Roosevelt Blvd., police said.

Seven employees who were trapped inside a quality-control room were unharmed, police said.

Two women were killed during the rampage, police said. They were not immediately identified.

One man removed from the building was shot in the neck and shoulder and was transported to Aria Health - Torresdale Campus, police said. A Kraft official said early Friday morning that a fourth person, a contract worker, was injured in less serious way.

The Kraft Foods plant, for many years known as the Nabisco factory, is where Kraft makes Ritz Crackers and Lorna Doone cookies.

"This is a sad day for the Kraft Foods family," Susan Davison, the company's director of corporate affairs, said in a statement e-mailed to The Inquirer. "We are very sad to report that two employees died as a result of this incident. Our thoughts and prayers go out to their families."

At 8:35 p.m., Hiller, who worked at the plant for 15 years, was suspended from her job and escorted from the premises, said Police Commissioner Charles H. Ramsey.

Nine minutes later, Hiller drove through a fence surrounding the plant and entered the building armed with a .357 magnum handgun, Ramsey said.

Hiller then went to the third-floor mixing room - where she worked as a mixer, coworkers said - and opened fire, Ramsey said.

"I don't know what her motive is and I don't want to guess," Ramsey said.

About 100 workers were reportedly inside the plant when the shooting occurred.

The seven employees who stayed behind were trying to hide from Hiller, Ramsey said. Several of them called 911 to describe their location and where Hiller was on the second floor.

When police arrived, Hiller fired one shot through a wall at three officers but they did not return fire, police said. At one point Hiller dialed 911 and spoke to a police operator.

After turning out the lights on the second floor, Hiller reportedly hunkered down in an office until she was apprehended by SWAT officers at 9:35 p.m.

A 57-year-old employee, who did not want to be named, said he was working on the second floor in the packaging department when someone ran in and yelled "Get out! Get out!" Then he heard a loud bang.

"I knew it was a gunshot," the man said.

As the employees ran out of the building, the police had already arrived and were running in, he said.

Tanya Bussey was at home in bed when she got a call from her sister, Valerie Johnson, 42, who works at the plant.

Her sister called to say someone was shooting and then the call was disconnected, Bussey said.

"I just started panicking," Bussey said, adding that she called another sister and went to the plant to find out if her sister was OK. She later found out that Valerie was unhurt.

Just after 1 a.m. Friday, police removed the bodies of the two victims from the plant.

Police said the plant would be closed overnight and delivery trucks were being turned away.

"We are working closely with the authorities as they investigate this situation, and our facility is closed until further notice," Kraft's Davison said. "This is a tragic loss for all of us. To assist our employees, we will be providing counseling services at the facility. At this time, we are still trying to confirm the facts. We again express our deepest condolences to the families who have been touched by this tragedy."

Contact staff writer Robert Moran at 215-854-5983 or bmoran@phillynews.com.