Police officers and security staff on duty at the Moscow airport hit by a deadly suicide bombing on Monday will be investigated for possible negligence, a law enforcement source said on Tuesday.

At least 35 people, including eight foreigners, were killed and another 180 injured in the attack. A total of 110 people have been hospitalized, with many in a critical condition.

Unconfirmed reports said the female suicide bomber was accompanied by a man whose head was ripped off by the blast.

The law enforcement source said security and police in the arrival zone were not alert enough to possible dangers.

"[Airport security officials] turned a blind eye to the presence of unauthorized persons," the source said.

The source said the security system in the area was poor despite earlier demands by officials to improve it. He said all the airport staff, many of whom come from Russian regions, must be checked.

Russian President Dmitry Medvedev earlier on Tuesday blamed the attack on a lapse in security at the airport and said airport officials should be held accountable.

However, a spokesman for Domodedovo said the airport's staff had "acted strictly in line with aviation security requirements."

A police source earlier told RIA Novosti that the security services were aware that terrorists were planning an attack on a Moscow airport, but were unable to locate and detain the three suspects they had been searching for.

This is not the first time Domodedovo has been targeted by terrorists. Two planes which took off from the airport, Moscow's busiest, were blown up by female Chechen suicide bombers in August 2004, killing a total of 90 people.

MOSCOW, January 25 (RIA Novosti)