HOUSTON (Reuters) - Valero Energy Corp said on Monday that the rupture of a small window on a unit at its 180,000 barrel-per-day (bpd) refinery in Memphis, Tennessee, injured two workers, but the incident did not involve an explosion or fire as some local media reports had indicated.

Valero spokesman Bill Day said the sight glass failed on an alkylation unit, injuring one Valero employee and a contractor. Refinery operations were not affected, Day said.

Memphis Fire Department spokesman Lt. Wayne Cook corroborated that there was no fire or explosion. He said both workers were taken to a hospital, one with critical injuries.

Cook and Day also said responders are investigating what chemicals were behind the glass that ruptured.

(Reporting By Kristen Hays; Editing by Gerald E. McCormick)