MONTERREY, Mexico (Reuters) - A "dirty bomb" alert in Boston last week was caused by a Mexican hoaxer trying to take revenge on Chinese immigrants who did not pay him for smuggling them across the U.S. border, Mexican prosecutors said on Wednesday.

The tip about a purported bomb plot involving Chinese nationals, which surfaced days before the Jan. 20 U.S. presidential inauguration, spurred a manhunt for 14 people and had police using radiation sensors in Boston's subway system.

Baja California state prosecutors said the tip was made by People trafficker Jose Ernesto Beltran, who called a law enforcement agency in California while high on drink and drugs to warn that a group of Chinese migrants planned to launch an attack.

"He was going to take the Chinese over (the U.S. border) but they didn't pay him," prosecutor's office spokesman, Moises Uribe, said by telephone from the city of Mexicali.

"He then took revenge by calling 911 in the United States and telling them that the group planned to carry out a terror attack on Boston," he added...