LOS ANGELES (Reuters) - Coroners conducted an autopsy on the body of conservative activist Andrew Breitbart on Friday but deferred a formal finding on the cause of his death until toxicology and lab tests are completed, officials said.

Los Angeles County Coroner's spokesman Craig Harvey said toxicology and microscopic tissue studies were ordered because of Breitbart's death at the relatively young age of 43.

They will take four to six weeks to complete, he said.

"It's standard procedure," Harvey said. "We have a very young man who died suddenly and unexpectedly, so we want to make sure we cover all the bases."

Breitbart, the founder of an influential conservative website named after himself and a lightning-rod of liberal criticism, died on Wednesday after collapsing on a sidewalk near his Los Angeles home.

A friend of Breitbart has told Reuters that the activist had a history of heart problems and was believed to have suffered a heart attack.

Harvey declined to comment on any findings of the autopsy, saying that the coroner's office was not releasing any preliminary information.

"We want to have a clear picture for everyone," before issuing any public findings, he said.

Breitbart, a brash and outspoken blogger and commentator, was at the center of several news websites including www.Breitbart.tv, www.breitbart.com and www.biggovernment.com.

Breitbart brought to national attention a sexually suggestive photo Democratic U.S. Representative Anthony Weiner posted through his Twitter page, fueling a scandal that eventually led to the congressman's resignation.

He also targeted ACORN, or the Association of Community Organizations for Reform Now -- posting videos in 2009 by conservative activists who secretly taped employees of the group giving tax advice to a couple posing as a pimp and a prostitute.

The controversy led Congress to deny federal housing funds to ACORN, which disbanded in 2010.

(Reporting by Dan Whitcomb; Editing by Cynthia Johnston)

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