Just after 1pm yesterday, police officers along with an Explosive Ordnance Disposal (EOD) team inspected the package at the Kerry Express Bang Khen branch on inbound Paholyothin Road.

They found in the box four M-67 grenades that had capacity to kill within a 5-to-10-metre radius.

The box was sent by a Bangkok man named Isarapong Phrombutr, who provided no postal address on the box, to the recipient identified only as “Max” who stayed at a house in Tambon Kud Ngong of Chon Buri’s Phanat Nikhom district.

It is reported that the names provided of the sender and the receiver were all fake. The identity card number provided by “Isarapong” was found to be that of Thanakorn Bunkarn, 28, of Ubon Ratchathani province.

Meanwhile, Prime Minister General Prayut Chanocha has instructed officers investigating the May 22 bomb blast at the Phramongkutklao Hospital in Bangkok not to give interviews about the case progress, a police source said.

They were told that only Deputy Prime Minister General Prawit Wongsuwan or national police chief Chakthip Chaijinda would be allowed to talk to the media, the source said.

However, Chakthip yesterday declined to give any comment on the case, saying the investigation team was working on it.

The hospital blast probe team recently found a person who may be a key witness in the case. A nurse said she saw a suspect carrying a backpack into the building shortly before the explosion, the source said.

Because of her information, officers were rechecking CCTV footage from cameras around the hospital, such as ATM machines, to find more clues, the source said.

They hoped to get confirmation on the person seen by the nurse, which would allow them to apply for an arrest warrant, the source said.

The hospital blast resulted to more than 20 injuries. The national police chief appointed his deputy, Pol General Srivara Rangsibhramanakul, to head the investigation into the hospital attack. More than 200 investigators are involved in the probe.