Image copyright Vacaville Police Department Image caption Adul Saosongyang was taken into custody after trying to claim the prize

California police have arrested a man accused of stealing a winning $10m (£7.8m) lottery ticket from his roommate as he slept.

Vacaville police say Adul Saosongyang, 35, was taken into custody as he attempted to claim the prize on Monday.

"That's definitely not the prize he was expecting," they wrote on Facebook on Tuesday after the suspect was charged with grand theft and booked into jail.

Police say the winner has yet to receive any of his winnings.

What exactly happened?

Police in Vacaville, about 35 miles (56km) outside Sacramento, detailed the man's alleged plot against his now-former roommate in their viral Facebook post.

They say the victim, who has asked not to be identified by police, purchased a $30 scratch-off ticket at a Lucky Grocery Store on 20 December "with hopes of winning a little extra cash for the holidays".

The man, who had mistakenly thought he had won $10,000 at first, "returned home and shared this wonderful news with his two roommates", according to investigators.

Image copyright Vacaville Police Department Image caption Adul Saosongyang, is accused of stealing his roommate's winning ticket

He went to collect his fortune the next day, but was told that his lottery ticket was not a winner.

Suspecting that his roommate had swapped it, he immediately called police to report the theft.

The following day, his roommate, Mr Saosongyang, reported to the Lottery's Sacramento district office, where investigators began their routine investigation as they do with all winnings over $600.

As part of their review process, lottery investigators visited the Lucky Grocery Store, where they were informed that the ticket may have been stolen.

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They contacted police and together determined Mr Saosongyang purchased a similar scratch-off card, altered and swapped it with the winning ticket while his roommate was sleeping.

On Monday Mr Saosongyang was "invited" to come collect his stolen winnings, investigators say, "but instead of him celebrating his big win he was arrested".

Police say the winner has not yet received his windfall, as the lottery completes their administrative investigation.