PARIS (AP) — France's interior minister said Sunday that there was a "kind of racism" behind the bombings of dozens of vacation homes on the French island of Corsica but stopped short of saying nationalist groups were responsible.

No one has claimed responsibility for the Friday night attacks and officials have not overtly pointed the finger. But several signs indicate there might have been a political motive behind the bombings.

While Corsica was definitively taken over by the French in the 18th century, it has significant autonomy and maintains a distinct language and culture. Homegrown nationalists have long pushed for more autonomy and have specifically lashed out at the influx of "continentals" from mainland France who flock each summer to the Mediterranean island known for its mountain vistas and rugged beaches.

Officials have said that the 26 homes targeted were mostly second residences, which often belong to mainland French. A graffiti tag of a separatist group was left on one of the houses hit, although the Paris prosecutor's office said it was too early consider that a claim of responsibility.

Interior Minister Manuel Valls, who is France's top cop, also declined to say who was behind the attacks, but he pinpointed at least one motive.

"There is without a doubt a kind of racism in the attacks," he said during an interview with journalists from television station iTele, Europe 1 radio and Le Parisien newspaper on Sunday morning.

The Paris prosecutor is investigating the bombings, including the possibly involvement of terrorist organizations and gangs.

Valls also criticized Corsican politicians for not sufficiently condemning the attacks — implying they may have some sympathy with the perpetrators. He stressed that Corsica should not be seen as anything but wholly part of France.

"We can't accept that in a state of laws, in a democracy — whether in Corsica or elsewhere — that people use bombs for political expression," he said.

Corsica is also beset by criminal gangs, and Valls would not rule out their involvement; he said that there are links between the criminal element on the island and the nationalists.

This year, gangs have carried out a series of killings that has outraged France and prompted the government to vow to stamp out the violence that has long been allowed to simmer on the island. The same night that the houses were bombed, a man was shot dead in an apparently unrelated attack.

Valls vowed that the government would fight both mafia and nationalist violence.