The incident occurred in a cafeteria at the Kronospan plant in the canton of Lucerne at around 9am.
"There was a shoot-out with several dead and several injured," Urs Wigger, a spokesman for Lucerne cantonal police told Blick.ch, the online news site.
Employees at the plant had earlier been informed that production would be cut, according to media reports.
Kronospan AG, operator of the plant, is part of the family-owned Swiss Krono group, a firm involved in the production and finishing of wood materials.
2.37 More from news agency AFP:
Local newspaper Willisauerer Bote said the company had just announced it was cutting production after a poor logging season.
Witnesses quoted by local media said the shooting started in the factory canteen around 9am, as workers on an early shift took their lunch break.
The biggest gun massacre in recent Swiss history occurred in September 2001 in the central city of Zug, claiming 15 lives including that of the shooter.
A local man with a history of legal clashes with the authorities dressed in a fake police uniform attacked the regional parliament armed with several weapons including an assault rifle.
2.28 The press conference is now over.
2.27 Police could not yet say how the perpetrator had died. Nor could they reveal what weapon he had used in the attack.
2.23 Kronospan CEO Ludwig Scheiblreiter: "The perpetrator had worked with us for ten years. A calm man. He was not involved in any other known incidents," Blick quoted him as saying at the press conference.
2.20 Six people were seriously injured in the shooting, but a prosecution spokesman was unable to say whether their lives were in danger. A seventh person suffered minor injuries.
2.15 Police chief Daniel Bussmann said the shooter was "a long-time Kronoswiss employee, 42 years old. His motive is not yet known and is the subject of an investigation," Blick.ch reports.
2.09 Witnesses have said the shooter was a former kickboxer who worked as a machine operator for Kronospan, according to newspaper Neue Luzerner Zeitung.
2.05 The press conference has been delayed slightly but is due to start in the next few minutes.
1.47 “We’re all in a state of shock,” Kronospan CFO Urs Fluder told Radio Pilatus.
“We’re doing everything humanly possibly to adequately console the [victims’] families and support them financially.”
1.33 This just in from news agency AFP:
Three helicopters from the Swiss emergency service REGA evacuated four seriously wounded people from the scene of the shooting at the Kronospan wood panel plant in Menznau, near Lucerne, a spokesman told AFP.
A police statement said that the perimeter had been sealed off, and that a hotline had been set up for families and employees.
A major police deployment was under way, the statement said, without giving details of the number of dead and injured.
A witness quoted by the local newspaper the Luzerner Zeitung said that an individual had entered the factory canteen and opened fire.
"This is a tragedy," Munzau's mayor, Adrian Duss, told AFP.
Owned by Austrian group Kronospan, the factory is the top employer in Munzau, employing around 400 people.
Switzerland has a longstanding tradition of gun ownership, and ranks third in the world for the number of guns per inhabitant, after the United States and Yemen.
On January 2nd, a 33-year-old drifter wielding two weapons killed three women and wounded two men in the village of Daillon in southern Switzerland.
1.11 Swiss daily Le Matin reports that the Mayor of Menznau has reacted with “profound distress” to the killings. “What has happened is unimaginable, incomprehensible and leaves me speechless,” he declared.
1.09 Cantonal police in Lucerne plan to hold a press conference about the shooting at 2pm.
1.05 This map shows the location of the Kronospan plant in Menznau.
12.53 A police hotline has been set up for employees and the families of people working at the plant: 041 248 83 83.
12.49 Police have sealed off a large area surrounding the plant.
12.46 Police have confirmed that seven people were injured in the shooting, some of them seriously.