A warrant for the arrest of Lindsay Lohan was issued today after the actor admitted failing a drug test.

The Mean Girls star faces a hearing on Friday that will determine whether she has violated her probation and, if so, whether she will be sent back to jail.

Superior court judge Elden Fox issued the arrest warrant in Beverly Hills, but Lohan will not be taken into custody prior to the hearing, court officials said.

Last month the judge threatened her with 30 days in jail for each probation violation. He must now decide whether to send the 24-year-old actor back to jail or back into treatment.

Lohan confirmed on her Twitter page last week that she failed a court-ordered drug and alcohol screening.

"Regrettably, I did in fact fail my most recent drug test," she tweeted.

She also said: "Substance abuse is a disease, which unfortunately doesn't go away over night. I am working hard to overcome it."

Lohan spent two weeks in prison earlier this year after being jailed for 90 days for violating her probation in a 2007 drug case. She was sentenced after she missed a string of alcohol education classes she was ordered to attend. Lohan spent another 23 days undergoing rehabilitation at Ronald Reagan UCLA medical centre.