By Laura Zuckerman

SALMON, Idaho (Reuters) - Former NFL quarterback Ryan Leaf, once a San Diego Chargers first-round draft pick, was arrested on Monday for the second time in three days in his hometown of Great Falls, Montana, on drug and theft charges, authorities said.

Leaf, 35, was jailed in Cascade County after police accused him of breaking into a mobile home on Sunday in the Great Falls area and stealing prescription drugs, including painkillers.

A search by police of Leaf's home revealed an additional 89 tablets of the painkiller hydrocodone in the pocket of Leaf's bathrobe, said Chris Hickman, detective sergeant with the Central Montana Drug Task Force.

Leaf, the No. 2 pick in the 1998 NFL draft after Peyton Manning, was charged with two counts of felony drug possession, misdemeanor theft and a probation violation.

Leaf had been released from the detention center on Friday on a $76,000 bond after police accused him of breaking into the home of an acquaintance in the Great Falls area and stealing prescription painkillers. He was charged with felony burglary and drug possession as well as misdemeanor theft.

The one-time Heisman Trophy finalist had been under investigation for some weeks before his arrest on Friday. The probe began after the U.S. Postal Service reported that Leaf was receiving numerous and suspicious packages from what appeared to be a warehouse for prescription drugs in Florida, Hickman said.

Police later found two bottles of prescription painkillers - one with no label and the other bearing the name of Leaf's friend - in the ex-quarterback's golf bag, Hickman said.

The arrests came just weeks after Leaf completed daily radiation treatments stemming from surgery last spring to remove a benign brain tumor.

"I know how hard Ryan has worked to get his life back," said Greg Witter, who co-authored the book, "596 Switch," with Leaf.

A supporter said on Saturday that Leaf had fought to conquer an addiction to painkillers brought on by a wrist injury that has plagued him since playing for the Cougars.

Representatives for Leaf and his family were not immediately available for comment.

Leaf's struggles with addiction came to public light three years ago when he faced drug charges in Texas. He was still on probation for those violations when arrested in Montana.

(Editing by Steve Gorman and Xavier Briand)