Karnataka Chief Minister Siddaramaiah on Friday said investigations are on to ascertain the cause and nature of the explosion at popular eatery Rameshwaram Cafe in Bengaluru on Friday, and added that it might have been caused by an 'improvised explosive device'.He said those involved will be found and strict action will be taken against them."According to the information I have got, after 12 P.M. someone placed a bag and went. Investigations are going on," Siddaramaiah said, adding that all the injured persons are out of danger.Speaking to reporters in Mysuru, he said, "CCTV and other things are being examined. We have come to know about someone placing a bag. It is said to be an improvised explosive blast. We have to see, the investigations are on."Asked whether it was a terrorist act, the CM said, it is not known and investigations are on. Police are at the spot and he has asked the Home Minister also to visit the spot."It was not a large-scale blast, it was an improvised explosive blast. Such things have happened earlier too, it should not happen. Let's see what it is. In recent times such blasts had not taken place other than the incident in Mangaluru during BJP rule. This is the first such incident during our government," he added.Stating that the incident should not be politicised and everyone should cooperate, Siddaramaiah said strict action would be taken against those involved.Asked if any high-level inquiry will be ordered, he said, "Let the things become clear. As of now we have information that the blast has taken place.""I have spoken to the police, they told me about the ongoing investigation. There was a small bag carried by a person. The identity of the person is not known. The cashier at the eatery is being questioned, as the person had gone to the cashier to take the token and ate the food...the same person had placed the bag," he added.Home Minister G Parameshwara said the Commissioner and Director General of Police have done a spot inspection to ascertain how the blast took place, who did it or whether it could have been an accident. Also the forensic team and bomb squad are at the spot.Speaking to reporters at Kunigal in Tumakuru district, he said, after gathering the samples, the reason for the blast will be known."According to the information I have received, about nine people are injured. All of them have been shifted to hospital and no one is serious," he said, adding that he will be visiting the spot either this evening or tomorrow morning.Responding to a question about reports that an improvised explosive device caused the blast, the minister said samples have been collected and, after verifying them, it would be ascertained and investigations will follow."There is information of a bag from which the explosion occurred, but we have to get the exact information from the department," he said, adding that he wouldn't like to speculate about the involvement of any organisation or anything.