"A man in his 40s, from East Anglia, has been arrested on suspicion of manslaughter," local police said in a statement.
"He is currently in police custody where he will be questioned by detectives."
It follows the charging Saturday of three other men with arson with intent to endanger life and five counts of manslaughter.
The accused -- all in their 30s and from Leicester, the nearby city of Coventry, and Oldham in north-west England -- will appear in court Monday.
Two other men, also in their 30s and from East Anglia, who were arrested on Friday were "released under investigation" over the weekend, police said.
The blast on February 25 near Leicester city centre destroyed a supermarket and a two-storey flat above it.
A 46-year-old woman and her two teenage sons were killed in the blast, along with one of their girlfriends, 18, and a 22-year-old woman.
Police, who have said there appeared to be no link to terrorism, have urged the media and public not to speculate about the cause of the explosion.
"With three people now charged and due in court, it becomes even more important, for legal reasons, that this message is heeded," Leicestershire police said Saturday.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)