The control system at the entrance of Moscow's Domodedovo International Airport was inadequate, Russia's Investigative Committee spokesman Vladimir Markin said on Tuesday.
"It has been established that the terrorist had no difficulties entering the arrival hall where the blast occurred as there was not an adequate control," Markin said.
Investigators are giving much attention to the circumstances preceding the blast, Markin said.
At least 35 people were killed and 180 injured in the suicide attack at Domodedovo airport's arrivals gate.
Markin also said a special group of investigators was examining documents on the airport's security and questioning Domodedovo managers responsible for security.
The bodies of the victims have been sent to Moscow's forensic bureau for identification, Markin said.
Earlier on Tuesday, a city health official said that about 30 victims of Monday's terrorist attack at the Moscow airport had been operated on overnight, and many remained in critical condition.
MOSCOW, January 25 (RIA Novosti)