In an unnerving reminder of the terrorist attacks on buses during the second intifada more than a decade ago, 21 people were injured, two critically, when a bomb exploded on Egged bus number 12 in Jerusalem’s Talpiot industrial area Monday afternoon causing a huge blaze.Remarkably, no deaths were reported following the carnage on Bar-Am Street, where two Egged buses and a third vehicle were reduced to skeletons of charred steel.After initial confusion about the cause of the inferno, police spokesman Micky Rosenfeld said a forensics team, aided by bomb disposal experts at the site, confirmed the fires were ignited by an explosive device.Reports circulated Monday night that one of the critically injured passengers was the one who detonated the bomb. “What we confirmed is that the remains of an explosive device were found on one of the buses,” said Rosenfeld.“We are still questioning people who are in the hospital to determine what happened moments before the explosion... We’re working carefully and cautiously to confirm whether it was a terrorist attack.”Rosenfeld said police were reluctant to confirm the explosion was a terrorist attack until an investigation by police and the Shin Bet (Israel Security Agency) was officially finalized.A first-responder said that the fires were reported at 5:45 p.m.“When the first call came in, it was involving two buses, and we immediately declared it a mass casualty incident,” said Daniel Katzenstein, an EMT and spokesman from United Hatzalah, while standing a few meters from the burned buses, and a charred blue car that caught fire.“We got there when the buses were fully engulfed, and it was not clear if the fire was from an explosion or some kind of [malfunction]. Volunteers from around the area rushed to scene.”Katzenstein said the victims were initially treated by ambucycle paramedics because ambulances were trapped in heavy traffic caused by the explosion.He said that all the victims were treated on site, and promptly transferred to Shaare Zedek Medical Center and Hadassah-University Medical Center in Ein Kerem and Mount Scopus. Late last night, 18 people were still hospitalized, seven in moderate condition and the rest lightly wounded.At the scene, dozens of officers and IDF personnel cordoned off the area for one kilometer in all directions, while over 100 paramedics, firemen and forensics specialists secured and investigated the area.A sea of white foam used by firefighters to put out the blazes remained next to the charred remains, surrounded by shattered glass from the buses’ windows. Hundreds of passersby stood nervously outside police lines attempting to learn what happened.Jerusalem Fire Department Team Leader Aric Abouloff, whose face was partially covered in soot, said six fire trucks, a tanker and rescue vehicle were dispatched to the scene.“The moment we got here we saw that one of the buses was completely on fire, and a private blue car next to it was also on fire,” he said.“A second bus behind the first bus also caught on fire, so we immediately started to put out the fires using foam, and after we put it out made a quick search inside the buses and vehicle to make sure that no one was trapped inside.”Abouloff said it took 30 minutes to put out the blazes, adding that he was astonished that no one was killed.“There was a lot of luck here today,” he said. “It could have been much worse.”On Monday night, Hadassah- University Medical Center spokeswoman Hadar Elboim said seven victims are being treated at its Ein Kerem hospital and three are at the Mount Scopus hospital.“Four of the patients at Ein Kerem are in moderate-to-serious condition and the three being treated at Mount Scopus are in light condition,” said Elboim.Meanwhile Shaare Zedek Medical Center spokeswoman Shoham Ruvio said one unidentified man, who is in critical condition, was undergoing emergency surgery at 9 p.m. “One man is in very, very critical condition, and we have two others in moderate condition and seven other in very light condition,” she said.Prime Minister Benjamin Netanyahu announced the explosion and fires to a stunned crowd during a speech marking the founding of the Irgun he delivered in Binyamina on Monday evening.“We will find whoever prepared and dispatched the explosives, as well as those who helped them,” he said. “We will settle accounts with these terrorists.”Herb Keinon contributed to this report.