Police say investigators have discovered another explosive at the Palestinian embassy complex in Prague where a possibly booby-trapped safe killed the ambassador, the Associated Press reports.

Spokesman Tomas Hulan confirmed the discovery Thursday, Jan 16, adding the unidentified explosive was sent for testing to Prague's Institute of Criminology. He declined to give details.

Police already had found 12 illegal weapons in a search following the Jan 1 explosion, prompting the Czech Foreign Ministry to accuse the Palestinians of breaching international obligations.

The Palestinians said the weapons were not illegal and dated to the Cold War.

Ambassador Jamal al-Jamal died after the safe exploded. The career diplomat had only started his posting in October. It remains unclear what caused the safe to explode but the ambassador's death is being investigated as a case of negligence.