Indian authorities have found the scooter used in one of the three bombings that shocked Mumbai Tuesday afternoon.

According to Indian Home Secretary R.K. Singh, the bombers planted an explosive inside a motorized scooter and parked it in a heavily populated location. Police have recovered the vehicle and are examining it for clues.

Police are also digging through surveillance videos and forensic evidence looking for any leads. They have collected dozens of CDs of closed circuit cameras and are examining the faces of everyone on tape to see if they are locals.

The videotapes might have already worked, and authorities have their first suspects. Three men, thought to be pretending to be strangers, made simultaneous cell phone calls at the same location about an hour before the bombs detonated. Police are examining the evidence.

The government quickly declared the bombings an act of terrorism, something with which the city of Mumbai is sadly familiar.

There is chaos everywhere. This must be a terrorist act as it happened in three places, senior Shiv Sena Party leader Manohar Joshi told reporters.

On Tuesday, three explosive devices were detonated during rush hour in heavily populated parts of the Mumbai, including a jewelry market and the area surrounding the Opera House. Eighteen people died in the blast and nearly 150 sustained moderate to severe injuries.

It is very unfortunate that once again Mumbai has to go through this... situation. I feel that the need of the hour is to take the injured to the hospital. Just when the feeling of confidence was developing in Mumbai. It has shaken up our city again, former Maharashtra Chief Minister Ashok Chavan told the press in India.

In his statement, Chavan was making a reference to a 2008 attack, when armed gunmen from Pakistan stormed Mumbai, killing 164 people.

According to local police, the explosion at the Opera House was the most powerful of the three.

Chief Minister of the Maharashtra state Prithviraj Chavan said Thursday that authorities will give 500,000 rupees ($11,230) to the family of the deceased, and 50,000 rupees for the hospital bills of the wounded.

Indian police held an emergency security meeting after the explosions.

Whoever has perpetrated this attack has worked in a very, very clandestine manner, Home Minister Palaniappan Chidambaram said at a news conference.

We are not pointing a finger at this stage, Chidambaram said. We have to look at every possible hostile group and find out whether they are behind the blast.