The FBI is investigating an incident in which an Ogden man said his mouth and throat were burned after he took a liquid diarrhea medicine.

A doctor told police that John Edward Vine, 66, had been burned by a caustic. The FBI is trying to determine if the product, Kaopectate, was tampered with, Ogden police said.Vine told Officer Gary Petersen the bottle's seal appeared intact but the cap removed very easily.

Kaye Bennett, a spokeswoman for The Upjohn Co. of Kalamazoo, Mich., which makes Kaopectate, said the company knew of the incident and was cooperating with the probe. Vine was in satisfactory condition at St. Benedict's Hospital, a spokeswoman said.

Vine's wife bought the Kaopectate Sunday at a Smith's store, authorities said. Smith's pharmacist Jeffery Nielsen said he has taken three bottles of the medicine off the store shelf. No others had the same lot number.

Petersen said a test of the Kaopectate showed it had a pH level of 3. Spencer Seager, a chemistry professor at Weber State College, said pH 3 is moderately acidic. He said lemon juice is pH 2.5 and vinegar is pH 3.3.