A man's body was found Tuesday afternoon in a car on the city's East side.
His body was discovered shortly after 1 p.m. in the 400 block of Rotary.
The man has not been identified.
San Antonio police said he was at a party on Monday night and went out to the car to sleep.
His friends checked on him later and told investigators he was OK. Then, when they went out to check on him on Tuesday, they say he was wasn't breathing.
Police say it could have been anything from the cold to alcohol poisoning.
They say the man's death does not appear suspicious.