(CNN) -- An employee killed two other people before fatally shooting himself at a lumber plant near the central Swiss city of Lucerne on Wednesday, local media reported.
Police said seven people were hurt in the attack, six of them seriously, according to the Lucerne-based daily Neue Luzerner Zeitung.
The gunman, age 42, had worked for a long time for Kronospan, a wood panel manufacturer in the village of Menznau, police said.
What led him to open fire with a handgun as employees were taking a morning break is not yet clear, but a hotline set up after the incident has been "widely used," according to a Lucerne police statement.
Rescuers flew four critically wounded people to two hospitals, air rescue spokeswoman Karine Hoerhager said.
The situation is under control, said Lucerne county police spokesman Urs Wigger, and officers have cordoned off a wide area around the factory.
The incident took place at 9 a.m. in Menznau, about 30 kilometers (19 miles) outside Lucerne. The factory employs 350 people, the newspaper said.
Local media reports suggest the plant has had to cut production because of a reduction in the timber harvest.
A spokesman for Kronospan in the United Kingdom said it had limited information about what happened.
"It's a terrible tragedy and our thoughts are with the families of the people who have lost their lives," he said.
Initial reports suggested the number of people killed might be higher. Police have yet to name the two people shot dead by the gunman.
Police have not determined whether the firearm was privately owned or issued by the military, the newspaper said.
Ismail Osman, a reporter for the newspaper, told CNNI's Michael Holmes that Switzerland's longstanding tradition of letting citizen-militia keep military-issued weapons has been questioned in recent years.
"It came to a pinnacle about two years ago, when we had a national vote if we should actually continue this tradition or not. An overwhelming majority said 'yes' to continuing that tradition. However, I'm sure the debate will pick up again after today," Osman said.
The Menznau Kronospan factory, which makes wood products under the brand name Kronoswiss, is one of 10 plants in seven countries run by the Swiss Krono Group, according to the company's website.
Its U.S. subsidiary, Kronotex USA, says on its website that the company has been a family business since its inception in 1897 in Austria, and its total annual sales exceed $1 billion.
CNN's Fred Pleitgen, Saskya Vandoorne and Carol Jordan contributed to this report. CNN's Laura Spark-Smith wrote from London, and Mark Morgenstein and Ben Brumfield wrote from Atlanta.