BEIJING — A North Korean shooter was stripped of his two medals and expelled from the Beijing Olympics along with a Vietnamese gymnast Friday after failing doping tests.

They are the second and third athletes caught doping in Beijing, where the IOC is conducting a record 4,500 drug tests.

The International Olympic Committee said shooter Kim Jong Su tested positive for propanolol after winning the silver medal in the 50-meter pistol and bronze in the 10-meter air pistol.

Propanolol is a banned betablocker, which can be used to prevent trembling in events such as shooting and archery.

The bronze medal in the 10-meter event now goes to American shooter Jason Turner. In the 50-meter event, China's Tan Zongliang moves up to the silver and Russia's Vladimir Isakov is upgraded to the bronze.

Gymnast Thi Ngan Thuong Do, who finished in last place in the women's floor exercise, tested positive for the diuretic furosemide.

IOC medical commission chairman Arne Ljungqvist said he considered Kim guilty of "a deliberate intake" of a banned substance because of propanolol's specific benefit for shooters. Kim could face a ban of up to two years from the international shooting federation.

Ljungqvist said he believed the Vietnamese gymnast inadvertently used furosemide, a common drug.

"My interpretation is this was probably the result of poor information given to the athlete, who did not have the knowledge of what to avoid and what she was allowed to take," he said.

IOC spokeswoman Giselle Davies said both athletes were kicked out of the games and had their accreditations revoked. Spanish cyclist Maria Isabel Moreno was kicked out of the games Monday after testing positive for EPO in a pre-competition check.