"The family is very concerned about her unexplained disappearance, especially given the fact that she has a serious medical condition and is in need of medical care," police said Thursday in a statement published by a number of news organizations.
Though Wren's father told CBS on Thursday that his daughter, 25, had been working as the "Saving Private Ryan" actor's assistant and living with him for about six months, Sizemore's manager, Charles Lago, said Friday that wasn't the case, adding that the two weren't romantically involved and that Sizemore is not a suspect in the case.
Bill Wren also told CBS that Megan has struggled with a drug addiction and was recently hospitalized for a staph infection.
"Tom has nothing to hide. ... She was not his assistant and didn't live at his place either," Lago told People magazine on Friday. "Megan could've never been his assistant, it's too demanding a job, and she was getting progressively worse due to heroin addiction over the last 18 months."
Lago said Sizemore, 49, had known Wren for a long time. "She used to live in the same building. ... He tried to help her."
Sizemore, who has struggled with drug addiction over the years and appeared on the third season of "Celebrity Rehab With Dr. Drew," was "very cooperative" with police when they questioned him recently, TMZ said. Sizemore has had a number of run-ins with the law, including a 2009 arrest on suspicion of domestic violence. In 2003, he was convicted of misdemeanor physical abuse and harassment of onetime madam to the stars Heidi Fleiss.
Wren was last seen on the afternoon of March 31 near Vermont Avenue and Wilshire Boulevard in L.A., police said.
Lindsay Lohan pleads no contest in necklace theft, has a June date with jail
-- Christie D'Zurilla
Photo: Tom Sizemore in 2005. Credit: Damian Dovarganes / Associated Press