“After two days of intense investigations, a family drama is the hypothesis favoured by the prosecutor in charge of the criminal investigation and the investigators,” police in the western Vaud region said in a statement.

Emergency services were alerted early Thursday after a massive explosion followed by a raging fire engulfed a detached house in the lakeside town of Yverdon-les-Bains, in Vaud canton.

The bodies of all five family members — a 45-year-old man, a 40-year-old woman and three girls aged five, nine and 13 — who lived there were eventually found in the rubble.

Autopsies determined that each had been shot, resulting in wounds that could have caused their deaths.

“A weapon was found near the father, who may have carried out the four other homicides, before ending his own life,” the police statement said.

There was so far no indication that anyone else had been involved, it added.

The cause of the fire had meanwhile not yet been formally established, the statement said.

However, police pointed out that “large quantities of accelerant, possibly gasoline” had been found in various rooms throughout the house.

“This could explain the level of damage to the building,” the statement suggested.