MANILA, Dec. 16 -- At least 21 people were killed and scores were wounded when a passenger bus fell from an elevated Skyway in Taguig City, Metro Manila, and allegedly landed into a van under the highway early Monday morning, a senior government official said.

Land Transportation Franchising Regulatory Board Chairman Winston Ginez said in a television interview that a Don Mariano Transit Bus fell from the south bound lane of the highway while on its way to Alabang, Muntinlupa City, at around 6:30 a.m. local time.

The driver of the van was reportedly one of those killed while the driver of the bus was one of the survivors, he said.

Ginez said the bus driver would undergo drug and alcohol test as investigators were yet to determine if the cause of accident was "human error, negligence or mechanical error."

The families of those who died in the accident would receive 75, 000 pesos (1,697 U.S. dollars) each while those injured would receive 15,000 pesos (339 dollars) each, he said.