MOSCOW — Relatives of people killed in a Russian airplane blown up over Egypt in October have filed a legal complaint to compel investigators to reveal their lines of inquiry into the cause of the crash. The complaint, filed in a Russian court, is the first sign of anger over an investigation that critics say has been influenced by politics.

The Kremlin has played down links between the crash and Russia’s air war in Syria, even though an affiliate of the Islamic State group claimed responsibility for downing the plane in retaliation for Russia’s involvement.

The lawyer for the relatives of the victims, Igor Trunov, said that the initial inquiry focused on mechanical problems and that the families had not been informed about whether the investigators had formally opened a terrorism case. The families could be entitled to additional insurance payments from a state insurer if investigators formally acknowledge that terrorism was the cause of the crash.