GENEVA — At least three people were killed in a shooting at a Swiss factory on Wednesday, the police said, adding that the gunman was among the dead. The episode was the second mass shooting in Switzerland this year.

The shooting occurred at about 9 a.m. in the canteen of a Kronospan wood processing factory in the town of Menznau, about 14 miles west of Lucerne, the police said in a statement. A spokesman for the police in Lucerne said that the gunman was a 42-year-old employee of the factory, but he gave no further details. The police said that the gunman was among those dead but that he was not shot by the police.

Seven people were injured in the shooting, the police said. The helicopter rescue service RGA said it evacuated four seriously injured people to hospital, the Swiss news agency SDA reported.

Mass shootings are uncommon in Switzerland, but the shooting in Menznau was the second such episode in two months, and it could revive debate on gun control in Switzerland, where it is estimated that there are between two and three million guns in circulation among the country’s population of eight million people.