Wayne Rooney's father and uncle have both been bailed following their arrest over an alleged betting scam.
Merseyside Police are investigating betting irregularities surrounding a Scottish Premier League match including Motherwell and Heart of Midlothian in December in which Jennings was sent off for dissent.
An earlier statement from Merseyside Police read: "Detectives have today executed warrants at 10 addresses across Merseyside and Glasgow and arrested nine men as part of an investigation into suspicious betting activity.
"The arrests are the culmination of a joint operation with the Gambling Commission and the nine who have been arrested for conspiracy to defraud are being interviewed by detectives.
"Those arrested are a 29-year-old from Bootle, a 48-year-old from West Derby, a 54-year-old from Norris Green, a 26-year-old from Croxteth, a 22-year-old from Kirkdale, a 31-year-old from Litherland, a 68-year-old from Fazakerley, a 36-year-old from Kirkby and a 26-year-old from Glasgow.
"The investigation relates to a match between Motherwell and Hearts on December 14 2010."