US federal authorities will review investigations into the deaths of two African-Americans who were found hanged from trees in California.

Local police had said there was no foul play in the deaths of Robert Fuller and Malcolm Harsch, who died in separate towns within two weeks of each other.

But people have raised fears the deaths may not have been suicides.

A petition for a thorough investigation into Mr Fuller's death has thousands of signatures.

His body was found hanging from a tree on 10 June in the town of Palmdale.

Officials said during a press conference that it appeared the 24-year-old had taken his own life.

However his family claim he was not suicidal.

"Everything that they've been telling us has not been right. My brother was not suicidal," Diamond Alexander, Mr Fuller's sister told a rally on Saturday.

Malcolm Harsch was found hanged from a tree at a homeless encampment in Victorville on 31 May. Officials there had said that the 37-year-old's death was likely to be a suicide. His official cause of death has not yet been given.

In a television interview his sister Harmonie Harsch said: "We are really just trying to get more answers as to what happened. My brother was so loving, not only to his family but even strangers. It is not like him."

In a statement to AP news agency, the FBI, US attorney's office in the Central District of California and the US Department of Justice's Civil Rights Division said that they were monitoring the investigations by the Los Angeles and San Bernardino County Sheriffs.

Both Sherriff's departments in Los Angeles County and San Bernadino said they would cooperate with investigators.

The men's deaths come as protests take place across the US calling for an end to racial inequality, racism and police brutality.