That impression was heightened yesterday with the revelation that police requested gas masks and protective gear the day before the attack.
Hirofumi Yusa, a public information officer for the Ground Self-Defence Forces, said military officials at Camp Asaka, north of Tokyo, loaned police several thousand gas masks and chemical warfare outfits and instructed officers in how to use them last Sunday.
Mr Yusa also said the unprecedented request was made because the police planned to raid several sites related to the Aum Shinri Kyo sect. He refused to comment further. Police refused to comment at all.
Reports in the Japanese media said the request was directly linked to fears that the Aum Shinri Kyo sect had the nerve gas sarin and might use it to repel the raids.
According to the Asahi television network, those raids were scheduled for last Wednesday.
Regional police departments were mobilised yesterday in the search for Shoko Asahara, leader of the apocalyptic cult. In a video shown on NHK, the Japanese national television station, Mr Asahara denied that substances found at the cult's headquarters had been used to make sarin. "We use them to make plastic products, fertilisers and insecticides," he said. The video, showing the squinting, bearded guru in his trademark purple pyjamas, was dispatched to NHK in response to a list of questions faxed to the cult's headquarters. Aum filed a claim for 30m yen (£210,000) for damage during police raids on Wednesday and Thursday.
Freedom of worship and the strict separation of religion and state are enshrined in Article 20 of the Constitution, and police have gone out of their way to avoid explicitly linking the sect with Monday's attack.
Since Tuesday, officers in protective suits have raided 25 Aum Shinri Kyo offices, including those in Tokyo and the mountain village of Kamiku Isshiki, and confiscated an astonishing quantity of chemicals, including several potential ingredients of sarin, used in Monday's attack. Chloroform and nitroglycerine were added to the list yesterday; television news has shown endless images of uniformed officers stacking lorries with boxes, barrels and aluminium containers.
But, ostensibly at least, the confiscations have been carried out in connection with allegations of kidnapping and forced detention which have dogged the cult for six years. A man with a sister in the sect disappeared from Tokyo on 28 February; a warrant for a 29-year-old male suspect was issued on Wednesday. A 23-year-old woman, Junko Shimizu, was wanted for questioning yesterday after an Osaka University student was allegedly abducted by Aum followers last week. And a doctor, Masayuki Hirata, 39, and three follow cultists were questioned by prosecutors yesterday amid claims that they drugged and locked up young recruits.
But no arrests have been made in the sarin case. Villagers in Kamiku Isshiki, near Mount Fuji, where Aum Shinri Kyo has its headquarters, spoke of the inadequacy of the police response, and their fears that troubles with the cult are not yet over.