Lohan has already had one period in rehab this year

She admitted herself to an "intensive medical rehabilitation facility", according to a statement released by her publicist.

Police said a "useable" amount of a substance thought to be cocaine was found in Lohan's car during her arrest.

The 20-year-old has not yet been charged but is due in court in August.

Substance abuse

Lohan was arrested Saturday morning after her car mounted a kerb and hit a shrub on Sunset Boulevard, Los Angeles.

A police spokesman said when officers arrived at the alleged incident, both Lohan and the vehicle were no longer at the scene. The car was then traced to a nearby apartment complex.

The actress has already had one stint in a rehabilitation this year, spending a month at the Promises treatment centre in Malibu.

Lohan had her first hit aged 11 in The Parent Trap. She has also starred in films like Freaky Friday, Mean Girls and A Prairie Home Companion.