Two people were killed and at least 15 injured on Saturday after a tanker plummeted off an interstate bridge and blew up in Baltimore. Fifty-five vehicles were involved in a mass collision at the time of the explosion, and as of Saturday afternoon authorities were still working to clear 40 cars, the Baltimore Sun reported. The incident is thought to have been caused by freezing rain covering the roads in ice, officials said, a factor that contributed to other car crashes in the area. Video showed the tanker flying down the highway, apparently sliding on the ice, before plunging through the wall and exploding, sending flames up into the sky. The identities of those killed have not yet been released. Nine of those injured were taken to the University of Maryland Shock Trauma Center. The cause of the crash is under investigation, as authorities say they are uncertain whether the pileup happened before or after the tanker explosion.