Steamy Love Triangle on 'Grindhouse' Set

(April 3) -- As if 'Grindhouse' didn't already have enough sex and scandal, reports of a no-holds-barred on-set affair between star Rose McGowan and married co-director Robert Rodriguez are giving the movie even more heat.

According to reports in Page Six, Rodriguez, who has been married for 16 years and has five children, was involved in an affair with McGowan, the former fiance of Marilyn Manson that became "the worst-kept secret on the set." Even worse, Rodriguez's wife was on-set for the entire duration, as she served as co-producer on 'Grindhouse.'

"They were going off to his trailer, having meals together," Page Six's source says. "Rose thought some of the crew were treating her differently, and the attitude was, like, well what do you expect when you're [bleeping] the director?"

When Rodriguez's wife found out about the fling, "there was an eruption of emotions - an emotional volcano," a source said.

Rodriguez and his wife are currently separated, but claim the split is amicable.