A suicide bomber Monday rammed his explosive-packed vehicle into the office of a Pakistan's investigation agency in the eastern city of Lahore and killed at least five people, police said.

Officials said that suspected militants were being interrogated in the Federal Investigation Agency (FIA) building.

The attack also injured up to 30 people, several are registered in critical condition.

Police said that guards at the building at the city's Model Town challenged the bomber but he detonated his vehicle.

No group has claimed responsibility for the attack. But suspected Taliban militants attacked the FIA building in Lahore in the past.

The FIA building was complete and the blast was so powerful that it caused damage to several nearby houses. Officials said that several employees of the FIA had been residing in the building. .

Windows of several buildings including a religious seminary were smashed, residents said.

Officials said that dozens of people were inside the FIA building when the bomb struck the office that took place at 8:15 a. m.. Officials said that the FIA had set up the office of its Special Investigation Unit in the building.

Ambulances rushed to the site and shifted the injured to several nearby hospitals. Locals also shifted the injured in private vehicles.

Rescue teams and the residents joined hands to pull the injured out of the rubble. Witnesses said that the blast created a 25-feet deep crater.

Pakistani Prime Minister Syed Yusuf Raza Gilani condemned the attack and asked the authorities to hold investigation into the attack.

District Police Officer Sajjad Bhutta visited the attack site and said that the authorities had taken security measures for the building but said that it is difficult for the police to stop suicide bombings.

Head of the nearby seminary said the residents had requested the government to shift the office from residential area but he complained that their request was not entertained.

Several schools, located in the area, were closed after the attack and parents rushed to schools to take their children.