By TAMMY WEBBER, Associated Press Writer

MELROSE PARK, Ill. (AP) - Gunfire broke out at a Navistar engine plant Monday morning, and five people were killed, authorities said.

No details were immediately available about the victims at the suburban Chicago plant.

Martin Reutimann, a 24-year-old engineer at the plant, said he was sitting at his desk at about 10 a.m. when the shooting erupted.

"I heard somebody yell 'There's a guy in the center aisle with a gun!"' The aisle is a long hallway where engines are tested, he said.

Reutimann said he didn't believe it at first, then saw people running past him. He grabbed his coat and cellular phone and said he heard gunshots as he dialed 911.

Five people died in the gunfire, the Cook County Medical Examiner's Office said.

Before the medical examiner's statement about the deaths, hospital officials said a 48-year-old man was pronounced dead on arrival at Gottlieb Memorial Hospital and a 45-year-old man was critically wounded with a gunshot to the abdomen. One other person was brought to Gottlieb, hospital spokeswoman Angie Hatfield said. Two others were taken to Loyola University Medical Center. One was listed in critical condition with a chest wound and one was in fair condition, spokesman Mike Maggio said earlier.

The plant, about 15 miles from the company's headquarters in downtown Chicago, employs about 1,400 people, Navistar spokesman Roy Wiley said. He did not have any details of the shooting.

The shooting came a month and a half after seven people were shot to death at a Wakefield, Mass., Internet consulting company, Edgewater Technology Inc. Software tester Michael McDermott is charged with murder in the Dec. 26 rampage. Authorities said the shooting may have stemmed from an Internal Revenue Service order to seize part of his wages to repay back taxes.

Navistar International is the nation's second-biggest producer of heavy-duty trucks, which it sells under the International brand. It also manufactures mid-sized trucks, school buses and diesel engines, which it also sells to Ford and other truck makers.

The company employs about 17,000 people and had $8.4 billion in sales last year. In December, it reported fourth-quarter profits were down 36 percent. The company announced 1,100 layoffs in August.

Navistar operates production plants in Canada, Mexico and the United States and has a contract manufacturing operation in Brazil. It exports its products to more than 70 countries and ranked No. 202 on the latest Fortune 500 list of America's biggest companies.