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A cache of unregistered weapons was found at a diplomatic residence where a Palestinian envoy was killed by an explosion, officials said Friday.

Ambassador Jamal al-Jamal died Wednesday after what authorities described as an accidental explosion involving the safe at his home in Prague, Czech Republic.

Officers searching the house following the blast found enough weapons to arm a ten-man combat unit, police said.

Local media reported that the haul included assault rifles. The guns had not been registered with Czech authorities.

Johana Grohová, spokeswoman for the country's Ministry of Foreign Affairs, told NBC News that the Czech government was "alarmed by the report of the Czech police." She said the unregistered arms could be a breach of the Vienna Convention and it will "demand" an explanation from the Palestinian authorities.

The Vienna Convention on Diplomatic Relations outlines the rules under which ambassadors operate within their host countries. It governs agreements such as diplomatic immunity.

Palestinian Ambassador to the Czech Republic Jamal al-Jamal, seen here with his wife, died in a blast at this diplomatic residence in Prague.AFP - Getty Images

A Palestinian official, speaking on condition of anonymity, told Reuters that the mission's staff had submitted the arms to the Czech authorities. He did not elaborate on the type of weapons involved, but said they had been retrieved from an old sack and had been untouched since Cold War times.

Czech police said they were not treating Wednesday's explosion as an attack or a terrorist incident. Officials said it could have been caused by a safety mechanism or by something detonating inside the vault.