Sabitri DandapatKaushik Basu being produced in Bankshal court on Wednesday. Picture by Sanat Kumar Sinha

Investigators are convinced from available evidence that it was Kaushik Basu, the owner of a cyber café, who had sent the terror mail on Tuesday evening that spread panic across Calcutta, forcing around 500 police personnel out on the streets.

Basu denies it. But he has not been able to offer any details about the four youths he said had used his Salt Lake cyber café immediately before the mail was sent.

Investigation revealed on Wednesday that Basu created an email ID, khalid50@rocketmail.com, under the assumed name of Khalid Mohammad about five minutes before despatching the mail that threatened to carry out bomb attacks in seven places in the city, including the high court.

After sending the mail that warned of blasts at 10pm, Kaushik tried to delete it.

“Since no other documents were either sent or received from this ID, it appears that he had created this exclusively to send the mail,” said an officer of the detective department.

The ID was created around 5.50pm and in the information one is required to provide for opening one Kaushik mentioned the date of birth — of the fake Khalid Mohammad — as March 25, 1900.

Kaushik, the father of two children, was arrested on Tuesday. A day later, the police detained Sabitri Dandapat, the domestic help of the Basu family, who ran the cyber café at the family’s IA block home in Kaushik’s absence. A Class VIII dropout, she has an Orkut profile and can type fast, the police said.

The officer said: “There are six terminals on the ground floor and one on the first and all of them are connected by LAN (local area network). We are trying to identify which terminal was used to send the mail. ”

Sabitri Dandapat

The police are examining if Sabitri, a divorcee in her mid-30s who has been with the family for over a decade, had any role in the incident.

Kaushik, who is an MBA, has been charged with waging war against the nation, criminal conspiracy and criminal intimidation and taken into police custody for 15 days.

The investigators are trying to find out how Kaushik knew the registration number of the car that land and land reforms minister Abdur Rezzak Mollah uses. In the mail, he had written that this vehicle would be used in the high court blast.