Confusion is growing over which terrorist group was really behind the Wednesday bombing of the New Delhi courthouse which killed at least twelve people and wounded dozens more.

Indian police have arrested three people in Srinagar (in Indian-administered Kashmir), including the owner of an internet café, in connection with an email sent to authorities which took responsibility for the blasts.

That email reportedly links the Delhi attack to Harkat-ul-Jihad Islami (HUJI), a militant group that is tied to al-Qaeda.

The email from HUJI stated: We own the responsibility of today's blast at the Delhi high court. Our demand is that Afzal Guru's death sentence should be repealed immediately as we would target major high courts and the Supreme Court of India.”

Guru was convicted of a December 2001 attack on India’s parliament and remains on death row. His scheduled execution has been postponed.

Based in Pakistan, HUJI (which means Islamic Struggle Movement) also has branches in Bangladesh and India itself.

The last known commander of HUJI was a man named Ilya Kashmiri, who was reportedly killed in June of this year by a U.S. military drone strike in North Waziristan in Pakistan.

However, in another email transmitted to Indian media sources in Mumbai and Delhi, a group called Indian Mujahideen (IM) took responsibility for the courthouse bombing and warned that it will also attack a shopping mall.

The missive from IM, written by someone named ‘Chotoo’ even declared that HUJI had no role in the bombing.

IM, which has taken responsibility for previous attacks in Jaipur, Varanasi and Delhi, was officially outlawed by the state in September 2008. The group is believed to be somehow connected to a group called ‘Students Islamic Movement of India’ (SIMI), which was formed in the 1970s. SIMI has explicitly stated that it wants to remove Western influences from India and convert the entire country into a Muslim state.

We are examining the email received by the media houses… about its authenticity and veracity and [we are] taking it seriously, said Secretary for Internal Security in the home ministry U.K. Bansal, in a statement.

The National Investigation Agency (NIA) security agency is also investigating the authenticity of the emails.

To complicate matters even further, other militant groups may have been complicit in the Delhi attack.

According to Indian media, police in Delhi received a warning on July 29 that Sikh militants might attack the city to avenge the conviction and imprisonment of Devinder Singh Bhullar, the leader of the Khalistan Liberation Front, a group that wants a separate homeland in the Punjab for Sikhs.

Still another possible culprit behind the bombing may be Pakistan-based Lashkar-e-Taiba (LeT).

According to reports, Indian investigators have proposed the theory that the Delhi blasts may have been a cooperative venture between two or three different terrorist groups. Perhaps LeT and IM provided logistical support to HUJI.

Some Indian investigators also postulate that Pakistan’s principal intelligence agency, Inter-Services Intelligence (ISI),might be the guiding force behind all these separate Muslim militant organizations.

Meanwhile, Indian police are preparing to interrogate senior HUJI commander Mohammed Amjad (also known as ‘Khwaja’) who is languishing in a jail in Hyderabad. Reportedly, Khwaja has already told Indian officials of HUJI’s “close relationship” with both LeT and ISI.