Three people were killed and four wounded in a rampage Monday morning at a company campus in southeast Albuquerque, the capital of U.S. state of New Mexico.

Earlier in the day, police chief Ray Schultz said six people were shot dead at Emcore Fiber Optics Corporation in Albuquerque.

He explained at a latest news conference that police officers on the scene had seen people down and believed they were dead and later found several shooting victims had survived.

Schultz released the updated number of people killed at an afternoon news conference, again confirmed four people were wounded.

Investigators say the incident occurred at around 9:30 a.m. in a conference room in the Emcore Fiber Optics building, adding that roads in the area have been closed down.

Police said the primary suspect is a 37-year-old employee of Encore Fiber Optics. It is believed he killed his ex-wife and another person before killing himself.

"In a situation like this, there are other people in the building and they became, unfortunately, casualties as well," Schultz said at the press conference.

Schultz also said the gunman was a former employee of the Albuquerque-based company which has about 700 full-time employees. But he did not release the name of the shooter.

The cause of the shooting not yet known, while the police said investigations are still underway.

But Schultz said police believe the incident was domestic violence shooting at workplace in nature. Schultz disclosed that the gunman had a history of domestic violence, saying there was at least one previous domestic violence call involving the gunman.

He believes that the gunman was the only killer who acted alone, and that a current employee of the firm, his wife or girlfriend, was the target of the attack.

Police said the man's children, who live out of Albuquerque, were taken into protective custody earlier Monday.

Chris Ramirez, director of communications for Albuquerque Mayor Richard Berry, also said the nature of the shooting is domestic.

"It appears it was some sort of domestic violence situation, but the information is still sketchy," said Ramirez. "Police are still collecting information from eyewitnesses."

Ramirez said Berry is at the site with executives of Emcore Corporation, a solar photovoltaic and fiber optics manufacturer based in Albuquerque.

"They are on site now working with employees," Ramirez said. "The Rio Rancho police, Albuquerque police, state police and the Bernalillo County Sheriff's Office are working together to piece together what happened this morning."

All those wounded were taken to University of New Mexico Hospital.

Billy Sparks, a University hospital spokesman confirmed that two victims were undergoing medical procedures and two others were considered stable.

More than 80 employees of the company have been taken in small groups to a nearby community center for police interviews.

Emcore Corporation makes compound semiconductor-based components and subsystems for the broadband, fiber optic, satellite and terrestrial solar markets.

Until recently, Emcore had employed about 500 in Albuquerque. The recession, however, led to layoffs since last year.