Alberto Del Rio Investigated for Domestic Battery, Paige Defends Him (Update)

1:07 PM PT -- Alberto's fiancee, Paige, is denying Alberto got physical with her and says the whole situation involved a 3rd party ... a female bystander who tried to take a picture.

"WE got the cops involved," Paige tweeted ... explaining, "I'm crying cuz I found out bad fam news & a lady tries take a pic. She gets angry throws a drink on [Alberto Del Rio]"

Paige continued, "Please leave us alone. That's it."

Wrestling superstar Alberto Del Rio -- aka Alberto El Patron -- is being investigated for an alleged domestic violence incident at a Florida airport ... TMZ Sports has learned.

We're told the Orlando PD was contacted around 3 PM on Sunday after Alberto -- real name Jose Rodriguez -- allegedly roughed up a female companion.

We spoke with witnesses who tell us Alberto and the woman were arguing in the terminal and when things escalated, cops were called.

As one witness put it, "There was an altercation."

Our law enforcement sources tell us Alberto has NOT been arrested and no charges have been filed -- investigators are still gathering information.

Cops would not confirm the name of the alleged victim. However, Alberto has been in a real-life relationship with WWE superstar Paige for a while and witnesses say she was at the airport with Alberto that day.

We reached out to Alberto's camp for comment -- so far, no word back.