Agra, Sep 18 (IANS): The low-intensity blast at a private hospital here was triggered by a "crude Improvised Explosive Device (IED)", police said Sunday adding the motive behind the attack, which injured at least four people, is still not confirmed.

"Preliminary investigations indicate it was a crude type of IED belt with an iron along with the explosive," Special Director General of Police Brij Lal told reporters here about the blast at Jai Hospital Saturday.

"With the nature of injuries caused, it appears the entire set-up that triggered the blast was locally prepared," he said.

"Six batteries of nine volt each were used. They were connected in series with some filament placed in the explosive. The blast took place due to the heating effect in the filament. We have found no traces of timer in the blast," he added.

However, the motive is not confirmed.

Deputy Inspector General of Police (Agra) Asim Arun told IANS: "We are yet to establish the motive behind the blast."

According to police sources, the state police in its report sent to the union home ministry late Saturday said they were trying to ascertain whether the blast was a terror strike or an attack due to some business rivalry as there were a number of private hospitals near Jai Hospital where the explosion took place Saturday evening.

A.K. Mishra, station house officer (SHO) of the Hari Parwat police station, which has jurisdiction of the blast site, told IANS: "No one has been detained in connection with the blast."

"Two of the four injured have been discharged from hospital," he added.

The explosion took place around 5.30 p.m. at the reception area of Jai Hospital, situated on a service lane of National Highway-2, barely 2.5 km from the Taj Mahal, a declared terror target frequented by thousands of tourists -- domestic and foreign.

Security at the 17th century Taj Mahal and other places has been beefed up.

In New Delhi, union Home Secretary R.K. Singh Saturday said reports indicated wires and battery parts were found at the blast spot.