At least 21 people were injured in an explosion on a Taiwan commuter train in the island nation's capital of Taipei, Friday morning. A man was spotted leaving a black backpack on the train and leaving moments before the explosion. Photo by Eivaisla/Shutterstock

TAIPEI, Taiwan, July 7 (UPI) -- At least 21 people were injured in an explosion on a Taiwan commuter train Thursday ignited by a pre-made explosive that resembled a firecracker, local media reported.

Investigators discovered a six-to-eight-inch "broken metal tube stuffed with explosive material inside a black backpack," said Taipei Police bomb squad chief Lee Tzu-wen.


The nation's official Central News Agency reported a man in his 40s was seen by a witness walking into the train and leaving a "black, long-shaped object." The blast occurred moments later.

The incident comes as the small island nation prepares for a super typhoon expected to reach land early Friday.