As details continue to surface about Lindsay Lohan's arrest for assault at a New York City night club, sources close to the actress are coming forward to reveal just how serious her substance abuse problem has been over the last few weeks.

Lohan was arrested this week after an incident at the bar Avenues, where the troubled 26-year-old actress punched a female patron in the face and was subsequently arrested for assault.

Witnesses said Lohan was drinking and doing cocaine on the night of the altercation, and now TMZ has reported that Lindsay has been out of control in recent days, drinking as much as two liters of vodka per day.

"According to sources, Lindsay's become so stressed by her dire financial situation and the impending probation violation -- stemming from her PCH crash this summer -- that she's turned to alcohol for relief," TMZ reported. "We're told Lindsay -- who's struggled with substance abuse in the past and even has a DUI conviction under her belt -- would often begin drinking first thing in the morning, and continue drinking throughout the day."

New reports from Perez Hilton reveal that onlookers who saw Lohan's behavior at the bar in New York Ciy's Chelsea neighborhood witnessed her drinking heavily and using drugs.

"She was drinking Grey Goose and also champagne. The vodka bottle was right in front of her. Lindsay was completely out of control. She was drinking way too much booze and was doing cocaine," said a source who was at the bar that night.

Things got tense between Lohan and a woman at the bar when the woman reportedly refused to make room for the actress in the club's VIP section, which infuriated Lohan. The actress then "sucker-punched" the woman and spit at her, according to reports.

Following the incident, Lindsay's father Michael Lohan has spoken out about his daughter's issues with substance abuse and her need for immediate help.

"She's got to get into treatment immediately. The drinking is out of control, it's literally out of control. And if anybody wants to deny that they're out of their minds. But I'm not going to be held accountable if this poor kid suffers any kind of demise or... I don't even want to go there," Michael Lohan said. "I believe it's alcohol, cocaine, and then taking pills to go to sleep - and I've heard that from a lot of people around her."

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