At least 21 people were killed and about 20 others were injured when a passenger bus fell from an elevated highway and landed on a van in suburban Manila, a Philippine police said, according to the Associated Press.

Police Superintendent Elizabeth Velasquez said the bus veered off the highway and slammed onto the van passing below in Paranaque city at dawn on Monday. Both drivers were killed. TV footaged showed bodies strewn around the bus wreckage while police investigated. The van was reduced to an unrecognizable pile of smashed metal.

Ivy Vadal, a spokeswoman of the corporation running the elevated Skyway -- the elevated highway where the accident occurred -- said that said it wasn't clear what caused the crash but added that road conditions were wet due to rain.