Men armed with assault rifles burst into a shoe factory and opened fire, killing at least 18 workers and wounding five, Honduran police said.
National police spokesman Leonel Sauceda called yesterday's attack in the northern city of San Pedro Sula "a massacre".
Authorities initially reported 15 dead, but assistant police commissioner Hector Ivan Mejia said three of the injured later died of their wounds.
San Pedro Sula was a hotbed of gunbattles between drug traffickers and among the country's Mara street gangs.
Mr Sauceda said at least four men using assault rifles were involved in the attack at the small shoe factory.
He said 23 employees were present and all were either killed or wounded.