A text message from Mel Gibson to Oksana Grigorieva in which he admitted, "Oksana, I wasn't safe for you last night," is a key part of the explosive domestic violence investigation into their January 6 bust-up, Breaking Celebrity News has learned exclusively.

The Lethal Weapon star sent the text the day after he allegedly punched Oksana twice in the head, and tried to choke her while she was holding their baby Lucia, who was two months old at the time.

Breaking Celebrity News first broke the story - with world exclusive photographs - that Oksana's mouth was badly damaged and she says it is from Mel punching her during a nuclear argument at the superstar's Malibu home.

Her dentist will support her claim that great force snapped off one veneer and cracked another on her upper front teeth.

We also broke the story Wednesday that Oksana was diagnosed with a concussion by another doctor, who could prove to be a powerful witness for her.

Gibson's lawyers have denied that he ever hit Oksana and have charged that the Russian-born muscian has tried to extort the Oscar-winning actor/director.

But this new text message seems to come extremely close to an outright admission of violence with Mel's confession that he wasn't "safe" for Oksana.

On audio tapes, obtained and released exclusively by Breaking Celebrity News, Mel told Oksana she "f*cking deserved it" when she complained that he hit her, while she was holding Lucia.