A police team visited a madrassa on the outskirts of Hyderabad on Thursday to ascertain the presence of any foreigners there, in the wake of the twin bomb blasts on Saturday, which killed 43 people.

However, authorities told the police that no foreigners were present at the madrassa, said sources. The madrassa authorities cooperated with the police, said the sources, but declined to give more details.

It is believed that the police were looking for information about a Bangladeshi national suspected to have links with external terrorist groups.

The police had earlier said that the twin blasts could be the handiwork of terror outfits based in Pakistan or Bangladesh.

The Hyderabad police have also questioned over 50 people, including some Pakistani and Bangladeshi nationals who were illegally staying in the city.

In a crucial step in the ongoing investigations, police on Wednesday released the sketch of a suspect in the bombing at Lumbini Park and offered a reward for any information on him.

Meanwhile, Lumbini Park was reopened for the public on Thursday. The park has been provided with additional security. Metal detectors have been installed at the entrance and all visitors are being searched before their entry.

"We will also install closed-circuit cameras and implement tight security measures to prevent any untoward incident," said an official.

However, Hyderabad continued to be rattled by hoax bomb threats on Thursday.

An engineering college on the outskirts of the city received an anonymous call about a bomb being planted in its premises. After a thorough search of the college premises, the police declared that it was a hoax call.