The military believes a network of 30 people including a Bangkok-based soldier has been selling military grenades by mail after eight M67 grenades were found with a courier in the capital on Friday.
A source said on Saturday that the military had been tracking as many as 30 people suspected of trading in grenades by taking orders from customers in many provinces.
An investigation led to the suspects after eight M67 grenades were found in two parcels at a Bang Khen district branch of Kerry Express in Bangkok. They had been returned there after employees could not find the intended recipient.
The sender's name was listed as Issarapong Prombutr. Soldiers later found that he was an innocent corporal whose name had been appropriated by the real sender. The source said the real sender was an engineering sergeant in Bangkok who had stolen grenades from a Bangkok army unit with the intention of selling them.
The source also said that 1st army commander Apirat Khongsompong had ordered tough actions against any soldier behind the thefts and illicit grenade trade, and against any supervisors who failed to prevent the crime.
Army spokesman Col Winthai Suvaree said commander-in-chief Chalermchai Sitthisat had ordered army units to cooperate with the police investigation into the grenade sales and check their weapons stocks.
The spokesman said, however, that authorities had not found any connection between the illegal grenade sale and three recent bombings in Bangkok.