Their romance was being categorized as a summer fling, but things appear to be more serious than previously believed between Michelle Rodriguez and Zac Efron.

Zac Efron Adores Michelle Rodriguez's 'Free-Spirit?'

In fact, the Neighbors actor was spotted leaving his girlfriend's home in Venice Beach early Sunday morning-tell-tale overnight bag in hand.

The two had also been spotted out together on Saturday night at popular West Hollywood hot spot Chateau Marmont, where they hung out with a group of friends.

Michelle Rodriguez & Zac Efron Just 'a Hook-Up?'

However, despite the two seeming to be more serious, a source told The Daily Mail that the couple actually are from having a serious relationship, something that works for both of them.

"They aren't dating per se, but I'm sure once they see each other again they might be all over each other again," a source said.

The two first caused a firestorm when they were spotted making out on a yacht in Sardinia, Italy over the July 4th weekend, but they've reportedly been hooking up on-and-off for years.

Hollywood Life reported on July 9 that the two have had a friends with benefits type of arrangement since 2011-not long after Efron broke up with his girlfriend of four years, Vanessa Hudgens in late 2010.

"Whenever they're together and both single, they hook up," a source told the website. "They're just having fun on vacation."

And despite the two reportedly spending the weekend together and seeming to be taking things more seriously, Rodriguez was spotted out without her new man once again on July 22, as she ventured out on her own to get a new haircut.

The actress debuted a sleek new style complete with a fringe on her Instagram account later that day-though her caption has stirred some controversy over whether or not she and Efron have hit some kind of rough patch.

"Finally got my hair bid. New Look New Life New Vibe washed yesterday right out of my hair looking forward baby," she captioned the photo.

Tags: Michelle Rodriguez Zac Efron