Los Angeles -- Police are searching for an art thief that made off with millions of dollars worth of paintings from inside an Encino home, including works by Marc Chagall and Diego Rivera.

Investigators say the thief entered the home near Ventura Boulevard and the (405) San Diego freeway the morning of August 23rd through an unlocked door while the maid was out, according to Los Angeles Police Detective Donald Hrycyk.

The paintings were taken from the walls of two rooms closest to the side door. The couple who lives at the residence was home at the time of the burglary, sleeping in another room at the back of the house, according to Hrycyk. The theft was discovered after the maid returned home.

The house is equipped with an anti-theft system, and had never been burglarized before, according to police.

The stolen paintings also include works by Hans Hofmann, Chaim Soutine, Arshile Gorky, Emil Nolde, Lyonel Feininger and Kees van Dongen.

The owners, whose names have not been released, are wealthy real estate investors who have been collecting art for nearly 50 years, according to police.

Investigators believe the thief or thieves were either familiar with the couple's routine or knew the maid would be out at the time of the burglary.

The pieces are worth hundreds of thousands of dollars each and would be difficult to sell, according to detectives unless the owner can prove it is the real thing.