NYC hotel livid after video of elevator scrap between Jay-Z and Beyonce's sister is leaked

A hip New York hotel said Monday it's investigating how surveillance video of Beyonce's sister Solange Knowles attacking brother-in-law Jay-Z in an elevator wound up on an Internet gossip site.

The fuzzy, silent black-and-white video posted on TMZ.com shows Solange kicking and hitting Jay-Z at the Standard hotel, site of an after-party following the glamorous Met Gala in New York on May 5.

A bodyguard is seen trying to restrain the clearly agitated 27-year-old singer, whose 32-year-old megastar sister stood largely in the corner alongside her 44-year-old husband of six years.

The trio can be recognized by the outfits they wore earlier that night at the Metropolitan Museum fashion gala -- Solange in a pink Phillip Lim dress, Beyonce in a sheer black Givenchy Haute Couture gown and Jay-Z in a white tuxedo jacket.

In an email to AFP, the Standard hotel in lower Manhattan expressed outrage that the three and half minute video had gone viral, and it threatened disciplinary and legal action once it finds who made it public.

"We are shocked and disappointed that there was a clear breach of our security system and the confidentiality that we count on providing our guests," it said.

"We are investigating with the utmost urgency the circumstances surrounding the situation and, as is our customary practice, will discipline and prosecute the individuals involved to our fullest capacity."

Neither Solange, Beyonce or Jay-Z mentioned the incident on their respective Twitter feeds Monday, and representatives did not immediately return calls asking for comment.

Solange, whose new album is due out later this year, performed at the Coachella music festival in California last month, where Beyonce joined her on stage, delighting fans.

The Met Gala after-party took place at the Standard's exclusive rooftop Top of the Standard lounge -- better known among New York night owls as "the Boom Boom Room."

The video, as posted online on Monday, can be seen below.