KYOTO -- The nation's latest poisoning case has exposed the lax controls over sodium azide and the inadequate records laboratories keep of its use.On Wednesday, eight doctors at Utano Hospital in Kyoto's Ukyo Ward became dizzy or vomited after drinking coffee and tea made from hot water drawn from an electric pot in which police later detected sodium azide.None of the victims was seriously hurt, but the unsolved incident marks the fourth sodium azide poisoning in three months, and the third to occur at a medical or scientific institution.Labs at the hospital's clinical research division situated next to the scene of the crime stored sodium azide on its shelves and in refrigerators for antiseptic uses, investigators say. They suspect the perpetrator likely stole the chemical from such a lab.Lab researchers rarely keep detailed records of how and when the chemical is used, police officials say, noting that such laboratories only have monitors for the chemicals during working hours, and that it is not uncommon for no one to be watching.On Tuesday, tea laced with sodium azide caused four people at the Okazaki National Research Institute in Aichi Prefecture to suffer nausea and headaches.On Oct. 16, six people became sick after drinking sodium azide-laced tea at a bioresource lab at Mie University, while in August, 10 workers at the Niigata branch of a wood preservative maker drank hot drinks made from hot water mixed with the substance.