Britney Spears' ex-husband Jason Alexander arrested after 'crashing' California wedding

Britney Spears' former husband crashed her wedding site in southern California, authorities say.

Ventura County Sheriff’s Captain Cameron Henderson said officers responded to a trespassing call after 2pm on Thursday.

He says the pop singer's first husband, Jason Alexander, was detained at the site of the ceremony.

Henderson says Alexander was arrested after officers noticed he had a warrant for his arrest in another county.

Alexander went on his Instagram live when he approached the event security.

In what appeared to be a mostly empty but decorated room, he told them Spears invited him.

"She’s my first wife, my only wife," said Alexander, who was briefly married to Spears – his childhood friend – in 2014. Their marriage lasted only 55 hours.

"I’m her first husband," he continued in the video. "I’m here to crash the wedding."

Spears was previously married to Kevin Federline, with whom she shares two sons, ages 14 and 15.

Spears and her fiancé Sam Asghari were reportedly expected to marry on Thursday.

The couple announced their engagement nearly nine months ago, after Asghari proposed with a four-carat diamond ring.

The couple met on the set of the Slumber Party music video in 2016.

A representative for Spears did not immediately return a request for comment.

Authorities are still investigating the reported trespassing.