MOMBASA, Kenya (AP) — A Kenyan court has found British national Jermaine Grant guilty of possessing bomb-making materials.

Sentencing will be on May 9. Grant is already serving a nine-year sentence for forging immigration documents.

Grant is believed to be part of an al-Shabab-linked cell that planned multiple attacks over Christmas in 2011.

Authorities say cell members include Samantha Lewthwaite, widow of Jermaine Lindsay, one of the bombers who killed 52 people on London’s transport system on July 7, 2005.