(CNN) -- A Russian lawmaker found stuffed in a barrel of cement last week may have been killed over unpaid debts, investigators said on Monday.

Mikhail Pakhomov, 36, was reported missing early last week, according to a report from the state-run RIA-Novosti news agency. On Thursday, some of the politician's personal property was found in a car searched during a traffic stop near Moscow. His body was later found in the barrel of cement in the basement of a private garage in a village near Moscow.

Pakhomov served in the city parliament in Lipetsk, a city of a half-million people about 700 kilometers (430 miles) south of Moscow. He was a member of the ruling United Russia party.

Twelve people have been arrested in connection with his death, investigators told RIA-Novosti.

The investigation continues, but investigators said Pakhomov may have been killed because of debts he had not paid off.