French police have reportedly arrested the sister and brother-in-law of Pascal Troadec, who disappeared along with his wife and two children in mid-February.

The mysterious vanishing, outside of the western French city of Nantes, has gripped the European nation, in part due to similarities between it and the 2011 mass murder of five members of the Dupont de Ligonnès family, whose bodies were found shot to death at their home in the same area. Sebastian Troadec, Pascal’s son and one of the missing, went to high school with one of the Dupont de Ligonnès victims. Xavier Dupont de Ligonnès, the husband and father of the dead, is the main suspect in the murder of his family and is a fugitive from the law.

READ also: ‘Frozen in Time’: Family’s sudden disappearance echoes a notorious murder mystery

According to the BBC, police reportedly detained Pascal Troadec’s sister and brother-in-law, who have not yet been identified, after items belonging to missing family members were found near their home in Brest, just under 200 miles away from Nantes.

The arrest came after 21-year-old Sebastian Troadec’s car was found in Saint-Nazaire on Thursday, on the French coast and on the way to Brest from Nantes. On Wednesday, pants and a social security card belonging to his younger sister were found in a wooded area in Brest.

The missing four are Pascal and Bridget Nantes, both around age 50, Sebastian, and Charlotte, 18.

Initially, there were indications that Sebastian may have been involved in the disappearance. While his car was missing from the home, the parents’ cars were still in the driveway. The beds in the home had been stripped, and no toothbrushes or hairbrushes were left behind.

“It’s as if the life of the house was frozen in time,” Prosecutor Pierre Sennes told The Guardian.

According to The Guardian, bloodstains were found on Sebastian’s phone, which was the last to be switched off among the four. The BBC reports that traces of blood were found on Brigitte’s watch, along with signs that blood was wiped away. The DNA from the blood samples reportedly matched three of the missing people, excluding Charlotte.

Sebastian was facing a sentence of community service for allegedly making death threats on his blog in 2013. According to The Guardian, sources who knew the family said that Sebastian had psychological problems and that Pascal suffered from depression.

Officials told the French newspaper Le Figaro that there is reason to believe some members of the family may still be alive.